CTE) (通用資料表運算式
適用于: Databricks SQL Databricks Runtime
定義暫存結果集,您可以在 SQL 語句的範圍內多次參考。 CTE 主要用於 SELECT
語句中。
語法
WITH common_table_expression [, ...]
common_table_expression
view_identifier [ ( column_identifier [, ...] ) ] [ AS ] ( query )
參數
view_identifier
可以參考 的識別碼
common_table_expression
column_identifier
選擇性識別碼,可供參考 的資料
common_table_expression
行。如果
column_identifier
指定了 ,則其數目必須符合 所query
傳回的資料行數目。 如果未指定任何名稱,則資料行名稱衍生自query
。-
產生結果集的查詢。
例子
-- 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