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

1. DELETE FROM table_name
2. [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。

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

创建的表customer_t1_bak，数据如下：

1. openGauss=# SELECT * FROM customer_t1_bak;
2. c_customer_sk | c_customer_id | c_first_name | c_last_name | amount
3. ---------------+---------------+--------------+-------------+--------
4. 3869 | hello         | Grace        |             |   1000
5. 3869 | hello         | Grace        |             |   1000
6. 3869 |               | Grace        |             |
7. 3869 | hello         |              |             |
8. 3869 | hello         |              |             |
9. |               |              |             |
10. 6985 | maps          | Joes         |             |   2200
11. 9976 | world         | James        |             |   5000
12. 4421 | Admin         | Local        |             |   3000
13. (9 rows)

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

1. openGauss=# DELETE FROM customer_t1_bak WHERE c_customer_sk = 3869;
2. DELETE 5

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

1. openGauss=# SELECT * FROM customer_t1_bak;
2. c_customer_sk | c_customer_id | c_first_name | c_last_name | amount
3. ---------------+---------------+--------------+-------------+--------
4. |               |              |             |
5. 6985 | maps          | Joes         |             |   2200
6. 9976 | world         | James        |             |   5000
7. 4421 | Admin         | Local        |             |   3000
8. (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。

1. openGauss=# DELETE FROM customer_t1_bak;
2. DELETE 4

得到结果如下。

1. openGauss=# SELECT * FROM customer_t1_bak;
2. c_customer_sk | c_customer_id | c_first_name | c_last_name | amount
3. ---------------+---------------+--------------+-------------+--------
4. (0 rows)