updating multiple columns using case statement in sql server

问题

I would like to update the table using case statement the query is like this...

select case(@columnname) when 'name1' then 
                                  begin
                                     update table
                                      set 
                                       pay1=pay1* 100
                                       pay2=pay2*20
                                       pay3=pay3* 100
                                  end
                        when 'name2' then 
                                       begin
                                     update table
                                      set 
                                       pay2=pay2*20
                                       pay3=pay3* 100
                                  end

                         when 'name3' then 
                                       begin
                                     update table
                                      set 
                                       pay3=pay3* 100
                                  end
                  end

can u please tell the correct logic to complete the query using case statement

回答1:

You'll have to swap the syntax around. The case statement will be applied for every value you want to update...

UPDATE table SET
    pay1 = CASE WHEN @columnname IN('name1') THEN pay1 * 100 ELSE pay1 END,
    pay2 = CASE WHEN @columnname IN('name1', 'name2') THEN pay2 * 20 ELSE pay2 END,
    pay3 = CASE WHEN @columnname IN('name1', 'name2', 'name3') THEN pay3 * 100 ELSE pay3 END

It looks like you actually want is a if statement....

IF @columnname = 'name1'
    UPDATE table SET pay1 = pay1 * 100, pay2=pay2*20, pay3=pay3* 100

ELSE IF @ColumnName = 'name2'
    UPDATE table SET pay2 = pay2 * 20, pay3 = pay3 * 100

ELSE IF @ColumnName = 'name3'
    UPDATE table SET pay3 = pay3 * 100

Hope that helps

回答2:

Use this.

  update table
               set pay1 = CASE WHEN @columnname = 'name1' 
                               THEN pay1* 100 
                               ELSE pay1
               set pay2 = CASE WHEN @columnname = 'name1' 
                                      OR @columnname = 'name2' 
                                THEN pay2* 20 
                                ELSE pay2
               set pay3 = CASE WHEN @columnname = 'name1' OR 
                                    @columnname = 'name2' OR 
                                    @columnname = 'name3' 
                                THEN pay3 * 100 
                                ELSE pay3

回答3:

You can use something like this :

UPDATE DBO.Test1
  SET val1=
   CASE name 
    WHEN 'name1' THEN val1*100 
    ELSE val1
   END,
  val2=
   CASE name 
    WHEN 'name1' THEN val2*20 
    WHEN 'name2' THEN val2*20
    ELSE val2
   END,
  val3=
   CASE name 
    WHEN 'name1' THEN val3*100 
    WHEN 'name2' THEN val3*100
    WHEN 'name3' THEN val3*100
    ELSE val3
   END;

I have used different 'When' clauses for updating val3. You can use single 'WHEN' for updating val3 since the value to be updated is same in all cases.

来源：https://stackoverflow.com/questions/27716671/updating-multiple-columns-using-case-statement-in-sql-server