mysql 插入時帶判斷條件

INSERT INTO table (f1 ,f2 ,f3)
SELECT 1 ,'a',3 FROM DUAL WHERE NOT EXISTS
    (SELECT 1 FROM table2 where a = b)

DUAL 為臨時表 ，也可以查找真實表字段插入。

需要插入多條數據時，可使用 UNION ：

INSERT INTO table (f1 ,f2 ,f3)
SELECT 1 ,'a',3 FROM DUAL WHERE NOT EXISTS
    (SELECT 1 FROM table2 where a = b)
UNION
SELECT 10 ,'ab',30 FROM DUAL WHERE NOT EXISTS
    (SELECT 1 FROM table2 where a = b)