Merge pull request #4687 from BohuTANG/doc-round3-not-in

chore(doc): add in conditional function and subquery operator

docs/doc/03-reference/02-functions/01-conditional-functions/in.md

@@ -0,0 +1,46 @@
+---
+title: IN
+description: Tests whether the argument is or is not one of the members of an explicit list
+---
+
+Tests whether the argument is or is not one of the members of an explicit list.
+
+## Syntax
+
+```sql
+<value> [ NOT ] IN ( <value1> , <value2> , ... )
+```
+
+## Arguments
+
+| Arguments   | Description |
+| ----------- | ----------- |
+
+## Return Type
+
+
+## Examples
+
+```sql
+mysql> select * from numbers(10) where number in (0, 1, 2, 3);
++--------+
+| number |
++--------+
+|      0 |
+|      1 |
+|      2 |
+|      3 |
++--------+
+
+mysql> select * from numbers(10) where number not in (0, 1, 2, 3);
++--------+
+| number |
++--------+
+|      4 |
+|      5 |
+|      6 |
+|      7 |
+|      8 |
+|      9 |
++--------+
+```

docs/doc/03-reference/03-sql/02-dml/_category_.json

@@ -0,0 +1,7 @@
+{
+  "label": "DML Commands",
+  "link": {
+    "type": "generated-index",
+    "slug": "/reference/sql/dml"
+  }
+}

docs/doc/03-reference/03-sql/03-query-syntax/_category_.json

@@ -0,0 +1,7 @@
+{
+  "label": "Query Syntax",
+  "link": {
+    "type": "generated-index",
+    "slug": "/reference/sql/query-syntax"
+  }
+}

docs/doc/03-reference/03-sql/04-query-operators/_category_.json

@@ -0,0 +1,7 @@
+{
+  "label": "Query Operators",
+  "link": {
+    "type": "generated-index",
+    "slug": "/reference/sql/query-operators"
+  }
+}

docs/doc/03-reference/03-sql/04-query-operators/operators-subquery.md

@@ -0,0 +1,64 @@
+---
+title: Subquery Operators
+description:
+  A subquery is a query nested within another query.
+---
+
+This topic provides reference information about the subquery operators supported in Databend.
+
+A subquery is a query nested within another query.
+
+## [ NOT ] EXISTS
+
+An EXISTS subquery is a boolean expression that can appear in a WHERE clause:
+* An EXISTS expression evaluates to TRUE if any rows are produced by the subquery.
+* A NOT EXISTS expression evaluates to TRUE if no rows are produced by the subquery.
+
+### Syntax
+
+```sql
+[ NOT ] EXISTS ( <query> )
+```
+
+:::note
+* Correlated EXISTS subqueries are currently supported only in a WHERE clause.
+:::
+
+### Example
+
+```sql
+mysql> select number from numbers(10) where number>5 and exists(select number from numbers(5) where number>4);
+Query OK, 0 rows affected
+```
+`select number from numbers(5) where number>4` no rows are produced, `exists(select number from numbers(5) where number>4)` is FALSE.
+
+```sql
+mysql> select number from numbers(10) where number>5 and exists(select number from numbers(5) where number>3);
++--------+
+| number |
++--------+
+|      6 |
+|      7 |
+|      8 |
+|      9 |
++--------+
+```
+
+`EXISTS(SELECT NUMBER FROM NUMBERS(5) WHERE NUMBER>3)` is TRUE.
+
+```sql
+mysql> select number from numbers(10) where number>5 and not exists(select number from numbers(5) where number>4);
++--------+
+| number |
++--------+
+|      6 |
+|      7 |
+|      8 |
+|      9 |
++--------+
+```
+
+`not exists(select number from numbers(5) where number>4)` is TRUE.
+
+
+

docs/doc/03-reference/03-sql/04-show/_category_.json

@@ -0,0 +1,7 @@
+{
+  "label": "SHOW Commands",
+  "link": {
+    "type": "generated-index",
+    "slug": "/reference/sql/show"
+  }
+}

docs/doc/03-reference/03-sql/05-kill/_category_.json

@@ -0,0 +1,7 @@
+{
+  "label": "KILL Commands",
+  "link": {
+    "type": "generated-index",
+    "slug": "/reference/sql/kill"
+  }
+}

docs/doc/03-reference/03-sql/06-list/_category_.json

@@ -0,0 +1,7 @@
+{
+  "label": "LIST Commands",
+  "link": {
+    "type": "generated-index",
+    "slug": "/reference/sql/list"
+  }
+}

docs/doc/03-reference/03-sql/07-system-tables/_category_.json

@@ -0,0 +1,7 @@
+{
+  "label": "System Tables",
+  "link": {
+    "type": "generated-index",
+    "slug": "/reference/sql/system-tables"
+  }
+}