informix replace null value with 0 in select

Question

I want replace null value with 0 and if not null i want to count the data ??

sql = "SELECT b.start,COUNT(a.resourceid)  " +
      "FROM t1 b,agentconnectiondetail a "+
      "WHERE TO_CHAR(a.startdatetime,'%R') >= TO_CHAR(b.start,'%R') AND TO_CHAR(a.enddatetime,'%R') <= TO_CHAR(b.finish,'%R') " +
      "AND a.resourceid = '"+dr[1].ToString()+"'" +
      "GROUP BY 1 ORDER BY 1";

that query output is null

what must I do ??

Answer 1

At first you should create simple query with simple db table, some values and requested result that clearly shows your problem.

Part 1: I want replace null value with 0

To change NULL into some value you can use NVL() function. Documentation says: The NVL expression returns different results, depending on whether its first argument evaluates to NULL.

Examples:

SELECT fld, NVL(fld, 0) FROM ...

Part 2: and if not null i want to count the data

SELECT COUNT(*) FROM ... WHERE fld IS NOT NULL

Answer 2

Are Start and finish both datetime datatypes ? If they are DATE then %R (HH:MM) is probably meaningless.

If they are Datetime then why not

SELECT b.start,COUNT(a.resourceid)  " +
  "FROM t1 b,agentconnectiondetail a "+
  "WHERE startdatetime  >= b.start AND a.enddatetime <= b.finish" +
  "AND a.resourceid = '"+dr[1].ToString()+"'" +
  "GROUP BY 1 ORDER BY 1";

If start and finish are dates then you can always extend() to be the same startdatetime and enddatetime