Common table expression (CTE) (Databricks SQL)

Defines a temporary result set that you can reference possibly multiple times within the scope of a SQL statement. A CTE is used mainly in a SELECT statement.

Syntax

WITH common_table_expression [, ...]

common_table_expression
  view_identifier [ ( column_identifier [, ...] ) ] [ AS ] ( query )

Parameters

  • view_identifier

    An identifier by which the common_table_expression can be referenced

  • column_identifier

    An optional identifier by which a column of the common_table_expression can be referenced.

    If column_identifiers are specified their number must match the number of columns returned by the query. If no names are specified the column names are derived from the query.

  • query

    A query producing a result set.

Examples

-- CTE with multiple column aliases
> WITH t(x, y) AS (SELECT 1, 2)
  SELECT * FROM t WHERE x = 1 AND y = 2;
   1   2

-- CTE in CTE definition
> WITH t AS (
    WITH t2 AS (SELECT 1)
    SELECT * FROM t2)
  SELECT * FROM t;
   1

-- CTE in subquery
> SELECT max(c) FROM (
    WITH t(c) AS (SELECT 1)
    SELECT * FROM t);
      1

-- CTE in subquery expression
> SELECT (WITH t AS (SELECT 1)
          SELECT * FROM t);
                1

-- CTE in CREATE VIEW statement
> CREATE VIEW v AS
    WITH t(a, b, c, d) AS (SELECT 1, 2, 3, 4)
    SELECT * FROM t;
> SELECT * FROM v;
   1   2   3   4

-- CTE names are scoped
> WITH t  AS (SELECT 1),
       t2 AS (
        WITH t AS (SELECT 2)
        SELECT * FROM t)
SELECT * FROM t2;
   2