The DELETE statement can be executed to delete rows that satisfy the WHERE clause from a specified table. If the WHERE clause does not exist, all rows in the table will be deleted and only the table structure is retained.
Syntax
DELETE FROM table_name
[WHERE condition];
Parameter Description
table_name
Specifies the name (optionally schema-qualified) of the target table.
Value range: an existing table name
condition
Specifies an expression that returns a Boolean value. Only rows for which this expression returns true will be deleted.
Examples
Create the customer_t1_bak table whose structure and data are the same as those of the customer_t1 table.
openGauss=# CREATE TABLE customer_t1_bak AS TABLE customer_t1;
INSERT 0 9
The customer_t1_bak table is created, and the data in the table is as follows:
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)
Run the following statement to delete the employee whose c_customer_sk is set to 3869 from the customer_t1_bak table:
openGauss=# DELETE FROM customer_t1_bak WHERE c_customer_sk = 3869;
DELETE 5
The following information is displayed, indicating that the row where c_customer_sk is set to 3869 has been deleted.
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)
If the WHERE statement is not specified, the data of the entire table is deleted by default, and only the table structure is retained.
openGauss=# DELETE FROM customer_t1_bak;
DELETE 4
The result is as follows:
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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