|
|
MYSQL - IF NOT EXISTS ... INSERT INTO 처리를 하려면 where에 넣어야 합니다.
아래의 쿼리는 제가 작성한 쿼리입니다.
간단히 ofgroupprop 테이블에 '0000007' 이 존재하지 않으면 insert하는 간단한 코드입니다.
MYSQL 설명
http://dev.mysql.com/doc/refman/5.0/en/exists-and-not-exists-subqueries.html
참고한 사이트
http://dotnetfish.blogspot.com/2011/11/mysql-if-not-exists-insert-into.html
12.2.9.6. Subqueries with EXISTS or NOT EXISTS
If a subquery returns any rows at all, EXISTS is subqueryTRUE, and NOT EXISTS is subqueryFALSE. For example:
SELECT column1 FROM t1 WHERE EXISTS (SELECT * FROM t2);
Traditionally, an EXISTS subquery starts with SELECT *, but it could begin with SELECT 5 or SELECT column1 or anything at all. MySQL ignores the SELECT list in such a subquery, so it makes no difference.
For the preceding example, if t2 contains any rows, even rows with nothing but NULL values, the EXISTS condition is TRUE. This is actually an unlikely example because a [NOT] EXISTS subquery almost always contains correlations. Here are some more realistic examples:
What kind of store is present in one or more cities?
SELECT DISTINCT store_type FROM stores WHERE EXISTS (SELECT * FROM cities_stores WHERE cities_stores.store_type = stores.store_type);What kind of store is present in no cities?
SELECT DISTINCT store_type FROM stores WHERE NOT EXISTS (SELECT * FROM cities_stores WHERE cities_stores.store_type = stores.store_type);What kind of store is present in all cities?
SELECT DISTINCT store_type FROM stores s1 WHERE NOT EXISTS ( SELECT * FROM cities WHERE NOT EXISTS ( SELECT * FROM cities_stores WHERE cities_stores.city = cities.city AND cities_stores.store_type = stores.store_type));
The last example is a double-nested NOT EXISTS query. That is, it has a NOT EXISTS clause within a NOT EXISTS clause. Formally, it answers the question “does a city exist with a store that is not in Stores”? But it is easier to say that a nested NOT EXISTS answers the question “is x TRUE for all y?”
|
|