在插入MySQL DB之前检查数据

Question

I am creating an SQL script that will add specific entries to the DB when run on a new environment. But I want to have to INSERT query insure that the data doesn't already exist before trying to insert it.

The query I came up with looks sound to me. But for some reason it gives me a syntax error. And yes I have RTFM'ed it. And I have Googled it. Based on other examples that I have seen (even here on Stack Exchange) it looks right to me. Can anyone identify what I am doing wrong?

Query:

INSERT INTO my_model (status, name) VALUES ('active', 'bbc')
WHERE NOT EXISTS (SELECT name FROM my_model WHERE name = 'bbc')

Any ideas?

Answer 1

The plain INSERT doesn't allow a WHERE . If the primary key is (status, name) then use INSERT IGNORE as @aynber exists. If not, try INSERT ... SELECT :

INSERT INTO my_model (status, name)
SELECT 'active', 'bbc'
FROM DUAL
WHERE NOT EXISTS (SELECT name FROM my_model WHERE name = 'bbc');

DUAL is a system-supplied one-row table, used to guarantee one row of results for something like SELECT 'active', 'bbc' FROM DUAL . It's an Oracle "invention" but supported in MySQL. You may be able to drop the FROM DUAL from the query; I don't have MySQL today so I can't test it to be sure.

Answer 2

try this:

INSERT INTO my_model (status, name) select('active', 'bbc') from my_model
WHERE NOT EXISTS (SELECT name FROM my_model WHERE name = 'bbc');

Answer 3

You want INSERT IGNORE instead of NOT EXISTS , if name is a primary/unique key. This will not insert anything if it hits a duplicate key error. You can also use ON DUPLICATE KEY UPDATE if you want to update a column if the row already exists.

Answer 4

in sql i would create a stored procedure not sure if you can in mysql

if !(SELECT name FROM my_model WHERE name = 'bbc') BEGIN INSERT INTO my_model (status, name) VALUES ('active', 'bbc') END