DESCRIBE OUTPUT

摘要

  1. DESCRIBE OUTPUT statement_name

说明

列出预编译语句的输出列，包括列名（或别名）、目录、模式、表、类型、类型大小（以字节为单位）以及表明列是否为别名的布尔值。

示例

预编译并描述一个具有四个输出列的查询：

  1. PREPARE my_select1 FROM
  2. SELECT * FROM nation
  1. DESCRIBE OUTPUT my_select1;
  1. Column Name | Catalog | Schema | Table  |  Type   | Type Size | Aliased
  2. -------------+---------+--------+--------+---------+-----------+---------
  3. nationkey   | tpch    | sf1    | nation | bigint  |         8 | false
  4. name        | tpch    | sf1    | nation | varchar |         0 | false
  5. regionkey   | tpch    | sf1    | nation | bigint  |         8 | false
  6. comment     | tpch    | sf1    | nation | varchar |         0 | false
  7. (4 rows)

预编译并描述一个输出列是表达式的查询：

  1. PREPARE my_select2 FROM
  2. SELECT count(*) as my_count, 1+2 FROM nation
  1. DESCRIBE OUTPUT my_select2;
  1. Column Name | Catalog | Schema | Table |  Type  | Type Size | Aliased
  2. -------------+---------+--------+-------+--------+-----------+---------
  3. my_count    |         |        |       | bigint |         8 | true
  4. _col1       |         |        |       | bigint |         8 | false
  5. (2 rows)

预编译并描述一个行计数查询：

  1. PREPARE my_create FROM
  2. CREATE TABLE foo AS SELECT * FROM nation
  1. DESCRIBE OUTPUT my_create;
  1. Column Name | Catalog | Schema | Table |  Type  | Type Size | Aliased
  2. -------------+---------+--------+-------+--------+-----------+---------
  3. rows        |         |        |       | bigint |         8 | false
  4. (1 row)

另请参见

PREPARE