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DELETE语句

DELETE语句可以从指定的表里删除满足WHERE子句的行。如果WHERE子句不存在,将删除表中所有行,结果只保留表结构。

语法格式

DELETE FROM table_name 
       [WHERE condition];

参数说明

  • table_name

    目标表的名称(可以有模式修饰)。

    取值范围:已存在的表名。

  • condition

    一个返回Boolean值的表达式,用于判断哪些行需要被删除。

示例

创建表customer_t1_bak,表的结构、数据与customer_t1一致。

openGauss=# CREATE TABLE customer_t1_bak AS TABLE customer_t1;
INSERT 0 9

创建的表customer_t1_bak,数据如下:

openGauss=# SELECT * FROM customer_t1_bak;
 c_customer_sk | c_customer_id | c_first_name | c_last_name | amount
---------------+---------------+--------------+-------------+--------
          3869 | hello         | Grace        |             |   1000
          3869 | hello         | Grace        |             |   1000
          3869 |               | Grace        |             |
          3869 | hello         |              |             |
          3869 | hello         |              |             |
               |               |              |             |
          6985 | maps          | Joes         |             |   2200
          9976 | world         | James        |             |   5000
          4421 | Admin         | Local        |             |   3000
(9 rows)

执行如下语句删除customer_t1_bak中c_customer_sk等于3869的职员。

openGauss=# DELETE FROM customer_t1_bak WHERE c_customer_sk = 3869;
DELETE 5

得到的结果如下,可以看到c_customer_sk = 3869的行已经被删除。

openGauss=# SELECT * FROM customer_t1_bak;
 c_customer_sk | c_customer_id | c_first_name | c_last_name | amount
---------------+---------------+--------------+-------------+--------
               |               |              |             |
          6985 | maps          | Joes         |             |   2200
          9976 | world         | James        |             |   5000
          4421 | Admin         | Local        |             |   3000
(4 rows)

不指定WHERE语句时,默认删除整张表的数据,仅保留表结构。

openGauss=# DELETE FROM customer_t1_bak;
DELETE 4

得到结果如下。

openGauss=# SELECT * FROM customer_t1_bak;
 c_customer_sk | c_customer_id | c_first_name | c_last_name | amount
---------------+---------------+--------------+-------------+--------
(0 rows)

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