MySql找出記錄的ID是否在另一個表中（在一個查詢中）

Question

可以說我有2張桌子：

Table 1: (customers)
------------------------------------------
id | name | etc... | etc..


Table 2: (blockList)
------------------------
id

我想知道每個客戶是否存在於blockList表中，因為我正在遍歷客戶表（在單個查詢中，作為單獨的字段）

像這樣： SELECT * FROM customers, blockList ORDER BY id DESC

Answer 1

您需要使用join，例如：

SELECT c.*, b.id AS id_blocklist
FROM customers AS c
LEFT JOIN blocklist AS b ON b.id = c.id
ORDER BY c.id DESC

如果只希望記錄在阻止列表中，請使用INNER JOIN

Answer 2

您必須指定表連接

SELECT * FROM customers as c, blockList as b WHERE c.id = b.id ORDER BY id DESC