Question

My colleague wrote this SQL statement and I had a hard time understanding it. What exactly is the purpose of using a colon in the where clause?

WHERE MGM_YYMM like :AS_YYMM

Full Query:

SELECT  A.MGM_YYMM,
        A.MGM_DATE,
        A.MGM_GB,
        A.INDATE,
        A.SUDATE,
        A.EMPNUM,
FROM  SE_MAGAM A(NOLOCK)
WHERE MGM_YYMM like :AS_YYMM
ORDER BY MGM_YYMM DESC

Answer 1

It is a bind variable.

The program (or whatever else is issuing the query) will assign a value to :AS_YYMM, in this case the pattern to match against the MGM_YYMM column.

These kind of parameterized queries are useful because they can be prepared/parsed/compiled/analyzed once and then be run multiple times for varying inputs with reduced overhead (compared to a new query each time). Also helps against SQL injection (compared to building a dynamic SQL statement from user input).