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 。

• 查詢

  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

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• 查詢