mysql如果不存在

Question

我來自MSSQL，現在使用Mysql，這可能是一個簡單的問題，但是如果不存在語句，您如何執行 。謝謝

IF NOT EXISTS(SELECT * from users WHERE Username = spUsername) 
    BEGIN 
    INSERT into users(ID,Username,Password,Email,Birthdate,DateJoin) 
      VALUES(UUID(),spUsername,spPassword,spEmail,spBirthDate,NOW()); 
    END 

Answer 1

我不是一個數據庫專家，但這是我如何做到這一點。

http://www.somethinghitme.com/2010/05/06/mysql-stored-procedures-if-not-exists/

DECLARE SomeId int; 
    DECLARE CheckExists int; 
    SET CheckExists = 0; 

    SELECT 1 INTO CheckExists from lookup_table WHERE someField = in_SomeParam LIMIT 1; 

    IF (CheckExists > 0) THEN 
     SELECT id INTO SomeId FROM lookup_table WHERE someField = in_SomeParam; 
    ELSE 
     INSERT INTO lookup_table (someField) VALUES(in_SomeParam); 
     SELECT SomeId = LAST_INSERT_ID(); 
    END IF;