MySQL選擇CONCAT條件

Question

我想在腦海里編譯這個...我有一個帶有firstname和lastname字段的表，我有一個像“Bob Jones”或“Bob Michael Jones”這樣的字符串和其他幾個字符串。

問題是，我在名字中有Bob，在姓氏中有Michael Jones

所以我想

SELECT neededfield, CONCAT(firstname, ' ', lastname) as firstlast 
  FROM users 
 WHERE firstlast = "Bob Michael Jones"

但它說未知的專欄“firstlast”..任何人都可以幫忙嗎？

Answer 1

您提供的別名用於查詢的輸出 - 它們在查詢本身中不可用。

您可以重復表達式：

SELECT neededfield, CONCAT(firstname, ' ', lastname) as firstlast 
FROM users
WHERE CONCAT(firstname, ' ', lastname) = "Bob Michael Jones"

或者包裝查詢

SELECT * FROM (
  SELECT neededfield, CONCAT(firstname, ' ', lastname) as firstlast 
  FROM users) base 
WHERE firstLast = "Bob Michael Jones"

Answer 2

試試這個：

SELECT * 
  FROM  (
        SELECT neededfield, CONCAT(firstname, ' ', lastname) as firstlast 
        FROM users 
    ) a
WHERE firstlast = "Bob Michael Jones"

Answer 3

SELECT needefield, CONCAT(firstname, ' ',lastname) as firstlast 
FROM users 
WHERE CONCAT(firstname, ' ', lastname) = "Bob Michael Jones"

Answer 4

使用CONCAT_WS（）。

SELECT CONCAT_WS(' ',firstname,lastname) as firstlast FROM users 
WHERE firstlast = "Bob Michael Jones";

第一個參數是其余參數的分隔符。

Answer 5

可以使用重復CONCAT表達式或使用子查詢的替代方法。 您可以使用HAVING子句來識別列別名。

SELECT 
  neededfield, CONCAT(firstname, ' ', lastname) AS firstlast 
FROM
  users 
HAVING firstlast = "Bob Michael Jones"

這是一個有效的SQL小提琴 。

Answer 6

嘗試：

SELECT neededfield, CONCAT(firstname, ' ', lastname) as firstlast 
  FROM users 
WHERE CONCAT(firstname, ' ', lastname) = "Bob Michael Jones"

除非您將查詢作為子選擇執行，否則您的別名firstlast在查詢的where子句中不可用。