Compare values of two columns then select the larger value

Question

I need to query a table and select 3 of the values of 4 columns. I need to compare the values of the 3rd column and the fourth column and select the larger value.

For ex

Answer 1

I would start by creating a view.

CREATE VIEW t_c
SELECT id, c1 AS c FROM t
UNION
SELECT id, c2 AS c FROM t;

Then I would select from that view.

SELECT id, MAX(c) FROM t_c GROUP BY id;

Answer 2

Just so we don't return null:

SELECT  IIF( a > b, a, COALESCE( a, b )) -- coalesce or isnull
FROM wherever

Here's a query to test it:

with whatever as (
  select null as a, 1 as b
  UNION
  select 1 as a, null as b
  union
  select 1 as a, 0 as b
  union
  select 0 as a, 1 as b
  union
  select null as a, null as b
)
select( iif( a > b, a, isnull( b, a )))
from whatever

Should return

null
1
1
1
1

Answer 3

In T-SQL the IF command is for programatic control. For example:

• IF x THEN doSQLStatement1 ELSE doSQLStatement2

Within a SQL statement, you need CASE.

CASE WHEN a > b THEN a ELSE b END

Answer 4

select column1, coloumn2, case when column3 < column4 then column4 else coloum3 end from table. 

Answer 5

Try this code:

SELECT column1, column2,
       (CASE WHEN column3 > column4 THEN column3 ELSE column4 END)
  FROM Table1

Result:

COLUMN1   COLUMN2  Hybrid
 hello     hello      5
  hi         hi       7

Here you have complete sample on SQL Fiddle.

Answer 6

You can use CASE, but if one of the values is 'null', the 'null' is considered the greatest value.

To solve this problem you can use GREATEST

SELECT GREATEST(column3, column4)
FROM Table1