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)