在WHERE子句中具有多个条件的Sql UPATE(Sql UPATE with multiple conditions in WHERE clause)

在WHERE子句中具有多个条件的Sql UPATE(Sql UPATE with multiple conditions in WHERE clause) UPDATE Table1 SET [Marks] = ( SELECT CASE STATEMENTS FROM Table2 T2 WHERE Table1.ID = T2.ID) )

上面的UPDATE语句工作正常，但如果ID不匹配，则为'Marks'插入NULL值。 但是如果Table1和Table2 ID不匹配，我想保留Table1中Marks的原始值。 我如何在我的代码中实现它。

我也试过使用WHERE EXISTS但仍然没有运气。 我想知道它的确切用法。

任何帮助非常感谢。

UPDATE Table1 SET [Marks] = ( SELECT CASE STATEMENTS FROM Table2 T2 WHERE Table1.ID = T2.ID) )

The above UPDATE statements works fine, but if the ID doesn't match then it insert NULL value for 'Marks'. But i wanted to keep the original value for Marks in Table1 if the Table1 and Table2 ID doesn't match. How do i implement that in my code please.

i also tried using WHERE EXISTS BUT STILL no luck. I wonder whats the exact use of it.

Any help much appreciated.

最满意答案

UPDATE Table1 SET [Marks] = ( SELECT CASE STATEMENTS FROM Table2 T2 WHERE Table1.ID = T2.ID) ) WHERE id IN (SELECT id FROM table2) UPDATE Table1 SET [Marks] = ( SELECT CASE STATEMENTS FROM Table2 T2 WHERE Table1.ID = T2.ID) ) WHERE id IN (SELECT id FROM table2)