Spark SQL ガイド

共通テーブル式 (CTE)

説明

共通テーブル式 (CTE) とは、SQL ステートメントのスコープ内で複数回参照できる可能性のある一時的な結果セットを定義するものです。CTE は主に SELECT ステートメントで使用されます。

構文

WITH common_table_expression [ , ... ]

common_table_expression は次のように定義されます。

expression_name [ ( column_name [ , ... ] ) ] [ AS ] ( query )

パラメータ

例

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

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

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

-- CTE in subquery expression
SELECT (
    WITH t AS (SELECT 1)
    SELECT * FROM t
);
+----------------+
|scalarsubquery()|
+----------------+
|               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;
+---+---+---+---+
|  a|  b|  c|  d|
+---+---+---+---+
|  1|  2|  3|  4|
+---+---+---+---+

WITH
    t AS (SELECT 1),
    t2 AS (
        WITH t AS (SELECT 2)
        SELECT * FROM t
    )
SELECT * FROM t2;
+---+
|  2|
+---+
|  2|
+---+