Cartesian Joins 笛卡兒聯接
SELECT *
FROM 表格A ,表格B
將表格所有可能聯接，全都資料聯接。
如果要限制，可以在WHERE加條件。
例：
SELECT *
FROM user AS u, occupation AS o
結果：
例：
SELECT *
FROM user AS u, occupation AS o
WHERE u.id = o.user_id
結果：
具有相同效果的JOIN語句是 CROSS JOIN
此JOIN不需要ON的條件限制，與table1,table2 效果相同
例︰
SELECT *
FROM user AS u CROSS JOIN occupation AS o
SELECT *
FROM user AS u CROSS JOIN occupation AS o
WHERE u.id = o.user_id
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