用大于、小于或等于参数化 SQL 语句

Question

I have a SQL report. I want to pass a new parameter to this and this parameter should decide below 3 outputs.

select * from po_distributions_all:

encumbered_amount is one of the column.

Parameter Value = P, return all rows with encumbered_amount values which are > zero

Parameter Value = N, return all with encumbered_amount values which are < zero.

Parameter Value = E, return all encumbered_amount values not equal to zero

Parameter as Blank, return all the rows.

I know I can achieve this by a union query.

Is there a way I can achieve without a union?

The query is already a lengthy one. For the simplicity of this question I mentioned it as a single line query above.

Answer 1

You could do this in the where clause:

WHERE
  (( :parameter = 'P' AND encumbered_amount > 0 ) OR
   ( :parameter = 'N' AND encumbered_amount < 0 ) OR
   ( :parameter = 'E' AND encumbered_amount != 0 ) OR
   ( :parameter IS NULL )
  )

Answer 2

What about dynamic SQL?

   sqlstr VARCAR2(1000);
   cur SYS_REFCURSOR;
BEGIN
   sqlstr := 'select * from po_distributions_all';
   IF Parameter = 'P' THEN
      sqlstr := sqlstr || ' WHERE encumbered_amount > 0';
   ELSEIF Parameter = 'N' THEN
      sqlstr := sqlstr || ' WHERE encumbered_amount < 0';
   ELSEIF Parameter = 'E' THEN
      sqlstr := sqlstr || ' WHERE encumbered_amount <> 0';
   ELSEIF Parameter IS NULL THEN
      NULL;
   ELSE
      RAISE VALUE_ERROR;
   END IF;

   OPEN cur FOR sqlstr;
   ...
END;

Answer 3

How about CASE expression? Could've been simpler if there were no E option:)

This is a SQL*Plus example; depending on tool you use, its '&&parameter' substitution variable could be :parameter or something else.

SQL> WITH
  2     po_distributions_all (encumbered_amount)
  3     AS
  4        (SELECT -200 FROM DUAL
  5         UNION ALL
  6         SELECT 100 FROM DUAL
  7         UNION ALL
  8         SELECT 0 FROM DUAL)
  9  SELECT *
 10    FROM po_distributions_all
 11   WHERE (   CASE
 12                WHEN    '&&parameter' <> 'E'
 13                     OR '&&parameter' IS NULL
 14                THEN
 15                   SIGN (encumbered_amount)
 16             END =
 17             CASE
 18                WHEN '&&parameter' = 'P' THEN 1
 19                WHEN '&&parameter' = 'N' THEN -1
 20                WHEN '&&parameter' IS NULL THEN SIGN (encumbered_amount)
 21             END
 22          OR CASE WHEN '&&parameter' = 'E' THEN encumbered_amount END <> 0);
Enter value for parameter: P

ENCUMBERED_AMOUNT
-----------------
              100

Negative values:

SQL> UNDEFINE PARAMETER
SQL> /
Enter value for parameter: N

ENCUMBERED_AMOUNT
-----------------
             -200

All values except zero:

SQL> UNDEFINE PARAMETER
SQL> /
Enter value for parameter: E

ENCUMBERED_AMOUNT
-----------------
             -200
              100

All values (parameter's value is NULL ):

SQL> UNDEFINE PARAMETER
SQL> /
Enter value for parameter:

ENCUMBERED_AMOUNT
-----------------
             -200
              100
                0

SQL>