MySQL數據在表左邊用什么?這是一個常見的問題,以下介紹幾種方法:
1. 使用UNION操作符:
SELECT 'Name' AS column1, 'Age' AS column2 UNION SELECT name, age FROM users;
2. 使用UNION ALL操作符:
SELECT 'Name' AS column1, 'Age' AS column2 UNION ALL SELECT name, age FROM users;
3. 使用LEFT JOIN操作符:
SELECT 'Name' AS column1, 'Age' AS column2, u.name, u.age FROM (SELECT 1) AS dummy LEFT JOIN users AS u ON 1 = 1;
4. 使用CROSS JOIN操作符:
SELECT 'Name' AS column1, 'Age' AS column2, u.name, u.age FROM (SELECT 1) AS dummy CROSS JOIN users AS u;
需要注意的是,以上方法中僅使用了一個虛擬表dummy,目的是為了讓查詢返回結果,因為UNION、JOIN等操作需要有結果集才能執行。
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