Use SQL statement to determine whether the record already exists before insert

Determine whether a record already exists before inserting a SQL statement

INSERT INTO test(A,B) select 'ab',2 
 WHERE NOT EXISTS (SELECT * FROM test WHERE A='ab');

Simple collection of judgments when inserting sql

When the user module or other modules require database uniqueness, you need to first determine whether the data already exists in the database before inserting it;

This is the most basic SQL insert statement.

```sql

```sql
INSERT INTO user(name,password) values(admin,123456)

Next, transform it into inserting to determine whether #{parameter} exists

```sql
INSERT INTO user(name, password)
SELECT #{admin},#{123456}
FROM DUAL WHERE NOT EXISTS
(SELECT name,password
FROM user WHERE name= #{admin} and password= # {123456});
``

This is done, the query return value = 0 means failure = 1 means success

The above is my personal experience. I hope it can give you a reference. I also hope that you will support 123WORDPRESS.COM.