Case-when statement in SQL

1. In the WHERE clause:

  1  create TABLE ' hello '. ' Sometbl ' ( Span style= "color: #008080;" > 2   3   ' id ' INT not NULL auto_increment,   5   6   7   ' B ' VARCHAR NULL,   8   9   ' C ' VARCHAR NULL,  10  11   PRIMARY KEY (' id '),  12  13  UNIQUE INDEX ' Id_unique ' (' id ' ASC); 

1 INSERT  into' Hello '. ' Sometbl ' (' A ', ' B ', ' C ')VALUES('1','1','0');2 3 INSERT  into' Hello '. ' Sometbl ' (' B ', ' C ')VALUES('1','1');4 5 INSERT  into' Hello '. ' Sometbl ' (' A ', ' C ')VALUES('1','1');6 7 INSERT  into' Hello '. ' Sometbl ' (' B ')VALUES('1');

There are two records in query a,b,c that meet the =1 criteria

SELECT *  fromHello.sometblwhere(( Case  whenA='1'  Then 1 Else 0 End)+( Case  whenB='1'  Then 1 Else 0 End)+( Case  whenC='1'  Then 1 Else 0 End))=2;

2. In select as a column

Output when ID 1,2,3,4, one, two, three, four

SELECTId Case  whenId=1  Then 'a' whenId=2  Then 'two' whenId=3  Then 'three' whenId=4  Then 'Four'Else 'other' EndChinese numerals fromHELLO.SOMETBL;

Output

Case-when statement in SQL