Determine if duplicate data is stored in the table before Oracle inserts data

Sometimes when inserting data with Oracle's database, you need to determine if the data already exists.

Our first idea is as follows: first execute the following SQL.

Select COUNT (*) isexists from t_test_lll;

Then determine if isexists equals 0 or not, and if it equals 0, insert is executed.

The above write, also can, but write a lot of code, not conducive to post-maintenance.

In fact, Oracle can be built into the INSERT statement to judge, the following SQL:

Insertwhen (Not EXISTS (select 1 from t_test_lll where id = ' 111 ')) Theninto t_test_lll (ID) SELECT ' 111 ' from dual;

This way, when there is a record of id= ' 111 ' in the database, the insert operation is not performed.

Determine if duplicate data is stored in the table before Oracle inserts data