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        <span>Presto 314 Documentation</span></a></h1>
    <h2 class="heading"><span>7.12. JSON Functions and Operators</span></h2>
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  <div class="section" id="json-functions-and-operators">
<h1>7.12. JSON Functions and Operators</h1>
<div class="section" id="cast-to-json">
<h2>Cast to JSON</h2>
<blockquote>
<div><p>Casting from <code class="docutils literal"><span class="pre">BOOLEAN</span></code>, <code class="docutils literal"><span class="pre">TINYINT</span></code>, <code class="docutils literal"><span class="pre">SMALLINT</span></code>, <code class="docutils literal"><span class="pre">INTEGER</span></code>,
<code class="docutils literal"><span class="pre">BIGINT</span></code>, <code class="docutils literal"><span class="pre">REAL</span></code>, <code class="docutils literal"><span class="pre">DOUBLE</span></code> or <code class="docutils literal"><span class="pre">VARCHAR</span></code> is supported.
Casting from <code class="docutils literal"><span class="pre">ARRAY</span></code>, <code class="docutils literal"><span class="pre">MAP</span></code> or <code class="docutils literal"><span class="pre">ROW</span></code> is supported when the element type of
the array is one of the supported types, or when the key type of the map
is <code class="docutils literal"><span class="pre">VARCHAR</span></code> and value type of the map is one of the supported types,
or when every field type of the row is one of the supported types.
Behaviors of the casts are shown with the examples below:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="k">NULL</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- NULL</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="mi">1</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;1&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="mi">9223372036854775807</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;9223372036854775807&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="s1">&#39;abc&#39;</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;&quot;abc&quot;&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="k">true</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;true&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="mi">1</span><span class="p">.</span><span class="mi">234</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;1.234&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="nb">ARRAY</span><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">23</span><span class="p">,</span> <span class="mi">456</span><span class="p">]</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;[1,23,456]&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="nb">ARRAY</span><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="k">NULL</span><span class="p">,</span> <span class="mi">456</span><span class="p">]</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;[1,null,456]&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="nb">ARRAY</span><span class="p">[</span><span class="nb">ARRAY</span><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">23</span><span class="p">],</span> <span class="nb">ARRAY</span><span class="p">[</span><span class="mi">456</span><span class="p">]]</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;[[1,23],[456]]&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">MAP_FROM_ENTRIES</span><span class="p">(</span><span class="nb">ARRAY</span><span class="p">[(</span><span class="s1">&#39;k1&#39;</span><span class="p">,</span> <span class="mi">1</span><span class="p">),</span> <span class="p">(</span><span class="s1">&#39;k2&#39;</span><span class="p">,</span> <span class="mi">23</span><span class="p">),</span> <span class="p">(</span><span class="s1">&#39;k3&#39;</span><span class="p">,</span> <span class="mi">456</span><span class="p">)])</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;{&quot;k1&quot;:1,&quot;k2&quot;:23,&quot;k3&quot;:456}&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="k">CAST</span><span class="p">(</span><span class="k">ROW</span><span class="p">(</span><span class="mi">123</span><span class="p">,</span> <span class="s1">&#39;abc&#39;</span><span class="p">,</span> <span class="k">true</span><span class="p">)</span> <span class="k">AS</span> <span class="k">ROW</span><span class="p">(</span><span class="n">v1</span> <span class="nb">BIGINT</span><span class="p">,</span> <span class="n">v2</span> <span class="nb">VARCHAR</span><span class="p">,</span> <span class="n">v3</span> <span class="nb">BOOLEAN</span><span class="p">))</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;[123,&quot;abc&quot;,true]&#39;</span>
</pre></div>
</div>
</div></blockquote>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Casting from NULL to <code class="docutils literal"><span class="pre">JSON</span></code> is not straightforward. Casting
from a standalone <code class="docutils literal"><span class="pre">NULL</span></code> will produce a SQL <code class="docutils literal"><span class="pre">NULL</span></code> instead of
<code class="docutils literal"><span class="pre">JSON</span> <span class="pre">'null'</span></code>. However, when casting from arrays or map containing
<code class="docutils literal"><span class="pre">NULL</span></code>s, the produced <code class="docutils literal"><span class="pre">JSON</span></code> will have <code class="docutils literal"><span class="pre">null</span></code>s in it.</p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">When casting from <code class="docutils literal"><span class="pre">ROW</span></code> to <code class="docutils literal"><span class="pre">JSON</span></code>, the result is a JSON array rather
than a JSON object. This is because positions are more important than
names for rows in SQL.</p>
</div>
</div>
<div class="section" id="cast-from-json">
<h2>Cast from JSON</h2>
<blockquote>
<div><p>Casting to <code class="docutils literal"><span class="pre">BOOLEAN</span></code>, <code class="docutils literal"><span class="pre">TINYINT</span></code>, <code class="docutils literal"><span class="pre">SMALLINT</span></code>, <code class="docutils literal"><span class="pre">INTEGER</span></code>,
<code class="docutils literal"><span class="pre">BIGINT</span></code>, <code class="docutils literal"><span class="pre">REAL</span></code>, <code class="docutils literal"><span class="pre">DOUBLE</span></code> or <code class="docutils literal"><span class="pre">VARCHAR</span></code> is supported.
Casting to <code class="docutils literal"><span class="pre">ARRAY</span></code> and <code class="docutils literal"><span class="pre">MAP</span></code> is supported when the element type of
the array is one of the supported types, or when the key type of the map
is <code class="docutils literal"><span class="pre">VARCHAR</span></code> and value type of the map is one of the supported types.
Behaviors of the casts are shown with the examples below:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;null&#39;</span> <span class="k">AS</span> <span class="nb">VARCHAR</span><span class="p">);</span> <span class="c1">-- NULL</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;1&#39;</span> <span class="k">AS</span> <span class="nb">INTEGER</span><span class="p">);</span> <span class="c1">-- 1</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;9223372036854775807&#39;</span> <span class="k">AS</span> <span class="nb">BIGINT</span><span class="p">);</span> <span class="c1">-- 9223372036854775807</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;&quot;abc&quot;&#39;</span> <span class="k">AS</span> <span class="nb">VARCHAR</span><span class="p">);</span> <span class="c1">-- abc</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;true&#39;</span> <span class="k">AS</span> <span class="nb">BOOLEAN</span><span class="p">);</span> <span class="c1">-- true</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;1.234&#39;</span> <span class="k">AS</span> <span class="n">DOUBLE</span><span class="p">);</span> <span class="c1">-- 1.234</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;[1,23,456]&#39;</span> <span class="k">AS</span> <span class="nb">ARRAY</span><span class="p">(</span><span class="nb">INTEGER</span><span class="p">));</span> <span class="c1">-- [1, 23, 456]</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;[1,null,456]&#39;</span> <span class="k">AS</span> <span class="nb">ARRAY</span><span class="p">(</span><span class="nb">INTEGER</span><span class="p">));</span> <span class="c1">-- [1, NULL, 456]</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;[[1,23],[456]]&#39;</span> <span class="k">AS</span> <span class="nb">ARRAY</span><span class="p">(</span><span class="nb">ARRAY</span><span class="p">(</span><span class="nb">INTEGER</span><span class="p">)));</span> <span class="c1">-- [[1, 23], [456]]</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;{&quot;k1&quot;:1,&quot;k2&quot;:23,&quot;k3&quot;:456}&#39;</span> <span class="k">AS</span> <span class="k">MAP</span><span class="p">(</span><span class="nb">VARCHAR</span><span class="p">,</span> <span class="nb">INTEGER</span><span class="p">));</span> <span class="c1">-- {k1=1, k2=23, k3=456}</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;{&quot;v1&quot;:123,&quot;v2&quot;:&quot;abc&quot;,&quot;v3&quot;:true}&#39;</span> <span class="k">AS</span> <span class="k">ROW</span><span class="p">(</span><span class="n">v1</span> <span class="nb">BIGINT</span><span class="p">,</span> <span class="n">v2</span> <span class="nb">VARCHAR</span><span class="p">,</span> <span class="n">v3</span> <span class="nb">BOOLEAN</span><span class="p">));</span> <span class="c1">-- {v1=123, v2=abc, v3=true}</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;[123,&quot;abc&quot;,true]&#39;</span> <span class="k">AS</span> <span class="k">ROW</span><span class="p">(</span><span class="n">v1</span> <span class="nb">BIGINT</span><span class="p">,</span> <span class="n">v2</span> <span class="nb">VARCHAR</span><span class="p">,</span> <span class="n">v3</span> <span class="nb">BOOLEAN</span><span class="p">));</span> <span class="c1">-- {value1=123, value2=abc, value3=true}</span>
</pre></div>
</div>
</div></blockquote>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p>JSON arrays can have mixed element types and JSON maps can have mixed
value types. This makes it impossible to cast them to SQL arrays and maps in
some cases. To address this, Presto supports partial casting of arrays and maps:</p>
<div class="last highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;[[1, 23], 456]&#39;</span> <span class="k">AS</span> <span class="nb">ARRAY</span><span class="p">(</span><span class="n">JSON</span><span class="p">));</span> <span class="c1">-- [JSON &#39;[1,23]&#39;, JSON &#39;456&#39;]</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;{&quot;k1&quot;: [1, 23], &quot;k2&quot;: 456}&#39;</span> <span class="k">AS</span> <span class="k">MAP</span><span class="p">(</span><span class="nb">VARCHAR</span><span class="p">,</span> <span class="n">JSON</span><span class="p">));</span> <span class="c1">-- {k1 = JSON &#39;[1,23]&#39;, k2 = JSON &#39;456&#39;}</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;[null]&#39;</span> <span class="k">AS</span> <span class="nb">ARRAY</span><span class="p">(</span><span class="n">JSON</span><span class="p">));</span> <span class="c1">-- [JSON &#39;null&#39;]</span>
</pre></div>
</div>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">When casting from <code class="docutils literal"><span class="pre">JSON</span></code> to <code class="docutils literal"><span class="pre">ROW</span></code>, both JSON array and JSON object are supported.</p>
</div>
</div>
<div class="section" id="json-functions">
<h2>JSON Functions</h2>
<dl class="function">
<dt id="is_json_scalar">
<code class="descname">is_json_scalar</code><span class="sig-paren">(</span><em>json</em><span class="sig-paren">)</span> &#x2192; boolean</dt>
<dd><p>Determine if <code class="docutils literal"><span class="pre">json</span></code> is a scalar (i.e. a JSON number, a JSON string, <code class="docutils literal"><span class="pre">true</span></code>, <code class="docutils literal"><span class="pre">false</span></code> or <code class="docutils literal"><span class="pre">null</span></code>):</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">is_json_scalar</span><span class="p">(</span><span class="s1">&#39;1&#39;</span><span class="p">);</span> <span class="c1">-- true</span>
<span class="k">SELECT</span> <span class="n">is_json_scalar</span><span class="p">(</span><span class="s1">&#39;[1, 2, 3]&#39;</span><span class="p">);</span> <span class="c1">-- false</span>
</pre></div>
</div>
</dd></dl>

<dl class="function">
<dt id="json_array_contains">
<code class="descname">json_array_contains</code><span class="sig-paren">(</span><em>json</em>, <em>value</em><span class="sig-paren">)</span> &#x2192; boolean</dt>
<dd><p>Determine if <code class="docutils literal"><span class="pre">value</span></code> exists in <code class="docutils literal"><span class="pre">json</span></code> (a string containing a JSON array):</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">json_array_contains</span><span class="p">(</span><span class="s1">&#39;[1, 2, 3]&#39;</span><span class="p">,</span> <span class="mi">2</span><span class="p">);</span>
</pre></div>
</div>
</dd></dl>

<dl class="function">
<dt id="json_array_get">
<code class="descname">json_array_get</code><span class="sig-paren">(</span><em>json_array</em>, <em>index</em><span class="sig-paren">)</span> &#x2192; json</dt>
<dd><div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p>The semantics of this function are broken. If the extracted element
is a string, it will be converted into an invalid <code class="docutils literal"><span class="pre">JSON</span></code> value that
is not properly quoted (the value will not be surrounded by quotes
and any interior quotes will not be escaped).</p>
<p class="last">We recommend against using this function. It cannot be fixed without
impacting existing usages and may be removed in a future release.</p>
</div>
<p>Returns the element at the specified index into the <code class="docutils literal"><span class="pre">json_array</span></code>.
The index is zero-based:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">json_array_get</span><span class="p">(</span><span class="s1">&#39;[&quot;a&quot;, [3, 9], &quot;c&quot;]&#39;</span><span class="p">,</span> <span class="mi">0</span><span class="p">);</span> <span class="c1">-- JSON &#39;a&#39; (invalid JSON)</span>
<span class="k">SELECT</span> <span class="n">json_array_get</span><span class="p">(</span><span class="s1">&#39;[&quot;a&quot;, [3, 9], &quot;c&quot;]&#39;</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span> <span class="c1">-- JSON &#39;[3,9]&#39;</span>
</pre></div>
</div>
<p>This function also supports negative indexes for fetching element indexed
from the end of an array:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">json_array_get</span><span class="p">(</span><span class="s1">&#39;[&quot;c&quot;, [3, 9], &quot;a&quot;]&#39;</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">);</span> <span class="c1">-- JSON &#39;a&#39; (invalid JSON)</span>
<span class="k">SELECT</span> <span class="n">json_array_get</span><span class="p">(</span><span class="s1">&#39;[&quot;c&quot;, [3, 9], &quot;a&quot;]&#39;</span><span class="p">,</span> <span class="o">-</span><span class="mi">2</span><span class="p">);</span> <span class="c1">-- JSON &#39;[3,9]&#39;</span>
</pre></div>
</div>
<p>If the element at the specified index doesn’t exist, the function returns null:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">json_array_get</span><span class="p">(</span><span class="s1">&#39;[]&#39;</span><span class="p">,</span> <span class="mi">0</span><span class="p">);</span> <span class="c1">-- null</span>
<span class="k">SELECT</span> <span class="n">json_array_get</span><span class="p">(</span><span class="s1">&#39;[&quot;a&quot;, &quot;b&quot;, &quot;c&quot;]&#39;</span><span class="p">,</span> <span class="mi">10</span><span class="p">);</span> <span class="c1">-- null</span>
<span class="k">SELECT</span> <span class="n">json_array_get</span><span class="p">(</span><span class="s1">&#39;[&quot;c&quot;, &quot;b&quot;, &quot;a&quot;]&#39;</span><span class="p">,</span> <span class="o">-</span><span class="mi">10</span><span class="p">);</span> <span class="c1">-- null</span>
</pre></div>
</div>
</dd></dl>

<dl class="function">
<dt id="json_array_length">
<code class="descname">json_array_length</code><span class="sig-paren">(</span><em>json</em><span class="sig-paren">)</span> &#x2192; bigint</dt>
<dd><p>Returns the array length of <code class="docutils literal"><span class="pre">json</span></code> (a string containing a JSON array):</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">json_array_length</span><span class="p">(</span><span class="s1">&#39;[1, 2, 3]&#39;</span><span class="p">);</span>
</pre></div>
</div>
</dd></dl>

<dl class="function">
<dt id="json_extract">
<code class="descname">json_extract</code><span class="sig-paren">(</span><em>json</em>, <em>json_path</em><span class="sig-paren">)</span> &#x2192; json</dt>
<dd><p>Evaluates the <a class="reference external" href="http://goessner.net/articles/JsonPath/">JSONPath</a>-like expression <code class="docutils literal"><span class="pre">json_path</span></code> on <code class="docutils literal"><span class="pre">json</span></code>
(a string containing JSON) and returns the result as a JSON string:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">json_extract</span><span class="p">(</span><span class="n">json</span><span class="p">,</span> <span class="s1">&#39;$.store.book&#39;</span><span class="p">);</span>
</pre></div>
</div>
</dd></dl>

<dl class="function">
<dt id="json_extract_scalar">
<code class="descname">json_extract_scalar</code><span class="sig-paren">(</span><em>json</em>, <em>json_path</em><span class="sig-paren">)</span> &#x2192; varchar</dt>
<dd><p>Like <a class="reference internal" href="#json_extract" title="json_extract"><code class="xref py py-func docutils literal"><span class="pre">json_extract()</span></code></a>, but returns the result value as a string (as opposed
to being encoded as JSON). The value referenced by <code class="docutils literal"><span class="pre">json_path</span></code> must be a
scalar (boolean, number or string):</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">json_extract_scalar</span><span class="p">(</span><span class="s1">&#39;[1, 2, 3]&#39;</span><span class="p">,</span> <span class="s1">&#39;$[2]&#39;</span><span class="p">);</span>
<span class="k">SELECT</span> <span class="n">json_extract_scalar</span><span class="p">(</span><span class="n">json</span><span class="p">,</span> <span class="s1">&#39;$.store.book[0].author&#39;</span><span class="p">);</span>
</pre></div>
</div>
</dd></dl>

<dl class="function">
<dt id="json_format">
<code class="descname">json_format</code><span class="sig-paren">(</span><em>json</em><span class="sig-paren">)</span> &#x2192; varchar</dt>
<dd><p>Returns the JSON text serialized from the input JSON value.
This is inverse function to <a class="reference internal" href="#json_parse" title="json_parse"><code class="xref py py-func docutils literal"><span class="pre">json_parse()</span></code></a>:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">json_format</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;[1, 2, 3]&#39;</span><span class="p">);</span> <span class="c1">-- &#39;[1,2,3]&#39;</span>
<span class="k">SELECT</span> <span class="n">json_format</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;&quot;a&quot;&#39;</span><span class="p">);</span> <span class="c1">-- &#39;&quot;a&quot;&#39;</span>
</pre></div>
</div>
</dd></dl>

<div class="admonition note">
<p class="first admonition-title">Note</p>
<p><a class="reference internal" href="#json_format" title="json_format"><code class="xref py py-func docutils literal"><span class="pre">json_format()</span></code></a> and <code class="docutils literal"><span class="pre">CAST(json</span> <span class="pre">AS</span> <span class="pre">VARCHAR)</span></code> have completely
different semantics.</p>
<p><a class="reference internal" href="#json_format" title="json_format"><code class="xref py py-func docutils literal"><span class="pre">json_format()</span></code></a> serializes the input JSON value to JSON text conforming to
<span class="target" id="index-0"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc7159.html"><strong>RFC 7159</strong></a>. The JSON value can be a JSON object, a JSON array, a JSON string,
a JSON number, <code class="docutils literal"><span class="pre">true</span></code>, <code class="docutils literal"><span class="pre">false</span></code> or <code class="docutils literal"><span class="pre">null</span></code>:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">json_format</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;{&quot;a&quot;: 1, &quot;b&quot;: 2}&#39;</span><span class="p">);</span> <span class="c1">-- &#39;{&quot;a&quot;:1,&quot;b&quot;:2}&#39;</span>
<span class="k">SELECT</span> <span class="n">json_format</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;[1, 2, 3]&#39;</span><span class="p">);</span> <span class="c1">-- &#39;[1,2,3]&#39;</span>
<span class="k">SELECT</span> <span class="n">json_format</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;&quot;abc&quot;&#39;</span><span class="p">);</span> <span class="c1">-- &#39;&quot;abc&quot;&#39;</span>
<span class="k">SELECT</span> <span class="n">json_format</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;42&#39;</span><span class="p">);</span> <span class="c1">-- &#39;42&#39;</span>
<span class="k">SELECT</span> <span class="n">json_format</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;true&#39;</span><span class="p">);</span> <span class="c1">-- &#39;true&#39;</span>
<span class="k">SELECT</span> <span class="n">json_format</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;null&#39;</span><span class="p">);</span> <span class="c1">-- &#39;null&#39;</span>
</pre></div>
</div>
<p><code class="docutils literal"><span class="pre">CAST(json</span> <span class="pre">AS</span> <span class="pre">VARCHAR)</span></code> casts the JSON value to the corresponding SQL VARCHAR value.
For JSON string, JSON number, <code class="docutils literal"><span class="pre">true</span></code>, <code class="docutils literal"><span class="pre">false</span></code> or <code class="docutils literal"><span class="pre">null</span></code>, the cast
behavior is same as the corresponding SQL type. JSON object and JSON array
cannot be cast to VARCHAR:</p>
<div class="last highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;{&quot;a&quot;: 1, &quot;b&quot;: 2}&#39;</span> <span class="k">AS</span> <span class="nb">VARCHAR</span><span class="p">);</span> <span class="c1">-- ERROR!</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;[1, 2, 3]&#39;</span> <span class="k">AS</span> <span class="nb">VARCHAR</span><span class="p">);</span> <span class="c1">-- ERROR!</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;&quot;abc&quot;&#39;</span> <span class="k">AS</span> <span class="nb">VARCHAR</span><span class="p">);</span> <span class="c1">-- &#39;abc&#39;; Note the double quote is gone</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;42&#39;</span> <span class="k">AS</span> <span class="nb">VARCHAR</span><span class="p">);</span> <span class="c1">-- &#39;42&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;true&#39;</span> <span class="k">AS</span> <span class="nb">VARCHAR</span><span class="p">);</span> <span class="c1">-- &#39;true&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="n">JSON</span> <span class="s1">&#39;null&#39;</span> <span class="k">AS</span> <span class="nb">VARCHAR</span><span class="p">);</span> <span class="c1">-- NULL</span>
</pre></div>
</div>
</div>
<dl class="function">
<dt id="json_parse">
<code class="descname">json_parse</code><span class="sig-paren">(</span><em>string</em><span class="sig-paren">)</span> &#x2192; json</dt>
<dd><p>Returns the JSON value deserialized from the input JSON text.
This is inverse function to <a class="reference internal" href="#json_format" title="json_format"><code class="xref py py-func docutils literal"><span class="pre">json_format()</span></code></a>:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">json_parse</span><span class="p">(</span><span class="s1">&#39;[1, 2, 3]&#39;</span><span class="p">);</span> <span class="c1">-- JSON &#39;[1,2,3]&#39;</span>
<span class="k">SELECT</span> <span class="n">json_parse</span><span class="p">(</span><span class="s1">&#39;&quot;abc&quot;&#39;</span><span class="p">);</span> <span class="c1">-- JSON &#39;&quot;abc&quot;&#39;</span>
</pre></div>
</div>
</dd></dl>

<div class="admonition note">
<p class="first admonition-title">Note</p>
<p><a class="reference internal" href="#json_parse" title="json_parse"><code class="xref py py-func docutils literal"><span class="pre">json_parse()</span></code></a> and <code class="docutils literal"><span class="pre">CAST(string</span> <span class="pre">AS</span> <span class="pre">JSON)</span></code> have completely
different semantics.</p>
<p><a class="reference internal" href="#json_parse" title="json_parse"><code class="xref py py-func docutils literal"><span class="pre">json_parse()</span></code></a> expects a JSON text conforming to <span class="target" id="index-1"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc7159.html"><strong>RFC 7159</strong></a>, and returns
the JSON value deserialized from the JSON text.
The JSON value can be a JSON object, a JSON array, a JSON string, a JSON number,
<code class="docutils literal"><span class="pre">true</span></code>, <code class="docutils literal"><span class="pre">false</span></code> or <code class="docutils literal"><span class="pre">null</span></code>:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">json_parse</span><span class="p">(</span><span class="s1">&#39;not_json&#39;</span><span class="p">);</span> <span class="c1">-- ERROR!</span>
<span class="k">SELECT</span> <span class="n">json_parse</span><span class="p">(</span><span class="s1">&#39;[&quot;a&quot;: 1, &quot;b&quot;: 2]&#39;</span><span class="p">);</span> <span class="c1">-- JSON &#39;[&quot;a&quot;: 1, &quot;b&quot;: 2]&#39;</span>
<span class="k">SELECT</span> <span class="n">json_parse</span><span class="p">(</span><span class="s1">&#39;[1, 2, 3]&#39;</span><span class="p">);</span> <span class="c1">-- JSON &#39;[1,2,3]&#39;</span>
<span class="k">SELECT</span> <span class="n">json_parse</span><span class="p">(</span><span class="s1">&#39;&quot;abc&quot;&#39;</span><span class="p">);</span> <span class="c1">-- JSON &#39;&quot;abc&quot;&#39;</span>
<span class="k">SELECT</span> <span class="n">json_parse</span><span class="p">(</span><span class="s1">&#39;42&#39;</span><span class="p">);</span> <span class="c1">-- JSON &#39;42&#39;</span>
<span class="k">SELECT</span> <span class="n">json_parse</span><span class="p">(</span><span class="s1">&#39;true&#39;</span><span class="p">);</span> <span class="c1">-- JSON &#39;true&#39;</span>
<span class="k">SELECT</span> <span class="n">json_parse</span><span class="p">(</span><span class="s1">&#39;null&#39;</span><span class="p">);</span> <span class="c1">-- JSON &#39;null&#39;</span>
</pre></div>
</div>
<p><code class="docutils literal"><span class="pre">CAST(string</span> <span class="pre">AS</span> <span class="pre">JSON)</span></code> takes any VARCHAR value as input, and returns
a JSON string with its value set to input string:</p>
<div class="last highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="s1">&#39;not_json&#39;</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;&quot;not_json&quot;&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="s1">&#39;[&quot;a&quot;: 1, &quot;b&quot;: 2]&#39;</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;&quot;[\&quot;a\&quot;: 1, \&quot;b\&quot;: 2]&quot;&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="s1">&#39;[1, 2, 3]&#39;</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;&quot;[1, 2, 3]&quot;&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="s1">&#39;&quot;abc&quot;&#39;</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;&quot;\&quot;abc\&quot;&quot;&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="s1">&#39;42&#39;</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;&quot;42&quot;&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="s1">&#39;true&#39;</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;&quot;true&quot;&#39;</span>
<span class="k">SELECT</span> <span class="k">CAST</span><span class="p">(</span><span class="s1">&#39;null&#39;</span> <span class="k">AS</span> <span class="n">JSON</span><span class="p">);</span> <span class="c1">-- JSON &#39;&quot;null&quot;&#39;</span>
</pre></div>
</div>
</div>
<dl class="function">
<dt id="json_size">
<code class="descname">json_size</code><span class="sig-paren">(</span><em>json</em>, <em>json_path</em><span class="sig-paren">)</span> &#x2192; bigint</dt>
<dd><p>Like <a class="reference internal" href="#json_extract" title="json_extract"><code class="xref py py-func docutils literal"><span class="pre">json_extract()</span></code></a>, but returns the size of the value.
For objects or arrays, the size is the number of members,
and the size of a scalar value is zero:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">json_size</span><span class="p">(</span><span class="s1">&#39;{&quot;x&quot;: {&quot;a&quot;: 1, &quot;b&quot;: 2}}&#39;</span><span class="p">,</span> <span class="s1">&#39;$.x&#39;</span><span class="p">);</span> <span class="c1">-- 2</span>
<span class="k">SELECT</span> <span class="n">json_size</span><span class="p">(</span><span class="s1">&#39;{&quot;x&quot;: [1, 2, 3]}&#39;</span><span class="p">,</span> <span class="s1">&#39;$.x&#39;</span><span class="p">);</span> <span class="c1">-- 3</span>
<span class="k">SELECT</span> <span class="n">json_size</span><span class="p">(</span><span class="s1">&#39;{&quot;x&quot;: {&quot;a&quot;: 1, &quot;b&quot;: 2}}&#39;</span><span class="p">,</span> <span class="s1">&#39;$.x.a&#39;</span><span class="p">);</span> <span class="c1">-- 0</span>
</pre></div>
</div>
</dd></dl>

</div>
</div>


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