TA貢獻1797條經驗 獲得超4個贊
首先INSTR（str, substr）是返回substr在str中的位置，若不存在，則返回0。select * from list ORDER BY INSTR('4,2,3,1',lid);
使用ORDER BY INSTR時，如果lid不存在'4,2,3,1'中，則返回0,order by默認按遞增排序，所以lid為4,2,3,1的會放到最后。SELECT * FROM EVENT WHERE eventId IN(443,419,431,440,420,414,509) ORDER BY INSTR(',443,419,431,440,420,414,509,',CONCAT(',',eventId,','))
mysql> select INSTR(',443,419,431,440,420,414,509,',CONCAT(',',443,','));
+------------------------------------------------------------+
| INSTR(',443,419,431,440,420,414,509,',CONCAT(',',443,',')) |
+------------------------------------------------------------+
| 1 |
+------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> select INSTR(',443,419,431,440,420,414,509,',CONCAT(',',419,','));
+------------------------------------------------------------+
| INSTR(',443,419,431,440,420,414,509,',CONCAT(',',419,',')) |
+------------------------------------------------------------+
| 5 |
+------------------------------------------------------------+
TA貢獻1836條經驗 獲得超13個贊
order by只是一個子句，instr是一個內部函數，用在你所列舉的例子中完全是作為order by子句的clause，語法上就是這么定義的，如果clause是表達式，先計算表達式，再根據表達式結果來執行order by.
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