#902 Support USE statement in ANSI (#950)

* Move USE statement from Snowflake to ANSI ⏪

* Add parser tests for USE statements in MySQL and Snowflake ✅

* Update CHANGELOG ✏️

* Fix due to decorator removed when merging

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix bug in L048 which flagged adjoining commas as failures.
 - Fix bug in L019 with inline comments.
 - Fix bug in L036 with multiple newlines.
+- Support "USE" statement in ANSI ([#902](https://github.com/sqlfluff/sqlfluff/issues/902)).
 - Parse explain statement ([#893](https://github.com/sqlfluff/sqlfluff/issues/893)).
 
 ## [0.5.1] - 2021-04-09

src/sqlfluff/dialects/dialect_ansi.py

@@ -2550,6 +2550,7 @@ class StatementSegment(BaseSegment):
         Ref("CreateModelStatementSegment"),
         Ref("DropModelStatementSegment"),
         Ref("DescribeStatementSegment"),
+        Ref("UseStatementSegment"),
         Ref("ExplainStatementSegment"),
     )
 
@@ -2600,6 +2601,29 @@ class DescribeStatementSegment(BaseSegment):
     )
 
 
+@ansi_dialect.segment()
+class UseStatementSegment(BaseSegment):
+    """A `USE` statement.
+
+    USE [ ROLE ] <name>
+
+    USE [ WAREHOUSE ] <name>
+
+    USE [ DATABASE ] <name>
+
+    USE [ SCHEMA ] [<db_name>.]<name>
+    """
+
+    type = "use_statement"
+    match_grammar = StartsWith("USE")
+
+    parse_grammar = Sequence(
+        "USE",
+        OneOf("ROLE", "WAREHOUSE", "DATABASE", "SCHEMA", optional=True),
+        Ref("ObjectReferenceSegment"),
+    )
+
+
 @ansi_dialect.segment()
 class ExplainStatementSegment(BaseSegment):
     """An `Explain` statement.

src/sqlfluff/dialects/dialect_snowflake.py

@@ -413,23 +413,6 @@ class SelectStatementSegment(ansi_dialect.get_segment("SelectStatementSegment"))
     )
 
 
-@snowflake_dialect.segment()
-class UseStatementSegment(BaseSegment):
-    """A snowflake `USE` statement.
-
-    https://docs.snowflake.com/en/sql-reference/sql/use.html
-    """
-
-    type = "use_statement"
-    match_grammar = StartsWith("USE")
-
-    parse_grammar = Sequence(
-        "USE",
-        OneOf("ROLE", "WAREHOUSE", "DATABASE", "SCHEMA", optional=True),
-        Ref("ObjectReferenceSegment"),
-    )
-
-
 @snowflake_dialect.segment()
 class CreateCloneStatementSegment(BaseSegment):
     """A snowflake `CREATE ... CLONE` statement.

test/fixtures/parser/mysql/use_database.sql

@@ -0,0 +1 @@
+use my_db;

test/fixtures/parser/mysql/use_database.yml

@@ -0,0 +1,7 @@
+file:
+  statement:
+    use_statement:
+      keyword: use
+      object_reference:
+        identifier: my_db
+  statement_terminator: ;

test/fixtures/parser/snowflake/snowflake_use.sql

@@ -0,0 +1,7 @@
+use role my_role;
+
+use warehouse my_warehouse;
+
+use database my_database;
+
+use schema my_schema;

test/fixtures/parser/snowflake/snowflake_use.yml

@@ -0,0 +1,29 @@
+file:
+- statement:
+    use_statement:
+    - keyword: use
+    - keyword: role
+    - object_reference:
+        identifier: my_role
+- statement_terminator: ;
+- statement:
+    use_statement:
+    - keyword: use
+    - keyword: warehouse
+    - object_reference:
+        identifier: my_warehouse
+- statement_terminator: ;
+- statement:
+    use_statement:
+    - keyword: use
+    - keyword: database
+    - object_reference:
+        identifier: my_database
+- statement_terminator: ;
+- statement:
+    use_statement:
+    - keyword: use
+    - keyword: schema
+    - object_reference:
+        identifier: my_schema
+- statement_terminator: ;