PRB: SQL SELECT Cursor Resultset Changes when Variable Changes

• Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0, 5.0a, 6.0

SYMPTOMS

The resultset of a cursor does not match the selection criteria from a SQL SELECT statement that includes a variable in the WHERE clause.

-or-

An error message similar to the one below is displayed when attempting to browse a cursor created with a SQL SELECT statement that includes a variable that is out of scope in the WHERE clause.

Variable 'MyVariable' not found

CAUSE

This behavior occurs when SET EXACT is set to OFF.

RESOLUTION

1. Set EXACT to ON.



2. Use a SQL SELECT statement that does not set a filter condition:




MyVariable="Test"
SELECT * FROM MyTable WHERE MyField=MyVariable AND .T. INTO CURSOR MyCursor 

MORE INFORMATION

Steps to Reproduce Behavior

1. Create a program file named DEMOPRG using the following code:




luExact_Value=SET('EXACT')
CLOSE ALL
IF !FILE('testa.dbf')
	CREATE TABLE testa (col1 c(5),col2 c(5))
	INDEX ON col1 TAG col1 OF testa
	INSERT INTO testa (col1,col2) VALUES ("1","a")
	INSERT INTO testa (col1,col2) VALUES ("2","b")
	INSERT INTO testa (col1,col2) VALUES ("3","c")
	INSERT INTO testa (col1,col2) VALUES ("3","d")
	INSERT INTO testa (col1,col2) VALUES ("4","e")
	INSERT INTO testa (col1,col2) VALUES ("4","f")
	INSERT INTO testa (col1,col2) VALUES ("5","g")
ENDIF
IF !FILE('testb.dbf')
	CREATE TABLE testb (col1 c(5),col2 c(5))
	INSERT INTO testb (col1,col2) VALUES ("1","a")
	INSERT INTO testb (col1,col2) VALUES ("2","b")
	INSERT INTO testb (col1,col2) VALUES ("3","c")
	INSERT INTO testb (col1,col2) VALUES ("3","d")
	INSERT INTO testb (col1,col2) VALUES ("4","e")
	INSERT INTO testb (col1,col2) VALUES ("4","f")
	INSERT INTO testb (col1,col2) VALUES ("5","g")
ENDIF
*!* SET EXACT ON
SET EXACT OFF
DO demoa WITH '1'
BROWSE TITLE DBF() TIMEOUT 10 && Get variable MyVariable_a not found message with the index

MyVariable="3"
DO demob
BROW TITLE DBF()+" Note values in COL1" TIMEOUT 10
MyVariable="2"
BROWSE TITLE DBF()+" Now note values in COL1" TIMEOUT 10

MyVariable="4"
DO alt_method
BROW TITLE DBF()+" Alternate Method Note values in COL1" TIMEOUT 10
MyVariable="3"
BROWSE TITLE DBF()+" Alternate Method Now note values in COL1" TIMEOUT 10
SET EXACT &luExact_Value
CLOSE ALL

PROCEDURE demoa
PARAMETER MyVariable_a
SELECT * FROM testa NOWAIT WHERE col1=MyVariable_a INTO CURSOR cursortesta

PROCEDURE demob
SELECT * FROM testa NOWAIT WHERE col1=MyVariable INTO CURSOR cursortesta

PROCEDURE alt_method
*!* This illustrates a SQL SELECT statement that does not set a filter condition
SELECT * FROM testa NOWAIT WHERE col1=MyVariable AND .T. INTO CURSOR cursortesta 

2. Run the program and note that when the first BROWSE command is executed, the following error message is displayed:

   Variable 'MyVariable_a' not found

   When this error message appears, select Ignore.



3. Note the number of records and the values displayed when the second BROWSE command is executed. The values displayed should be as follows:




col1	col2
3	c
3	d




4. Note the number of records and the values displayed when the third BROWSE command is executed. The values displayed should be as follows:




col1	col2
2	b




5. Note the number of records and the values displayed when subsequent BROWSE commands are executed. The values displayed should be as follows:




col1	col2
4	e
4	f




6. Change the following line of code from:

   SET EXACT OFF 

   to:




SET EXACT ON 

and re-run the program. Note that the Variable Not Found error message does not occur and also note that the second and third times the BROWSE command is executed the cursor resultset remains constant.

Additional query words:

Keywords : kbDatabase kbSQL kbVFp300b kbVFp500a kbVFp600 KbDBFDBC kbGrpFox kbDSupport
Version : WINDOWS:3.0,3.0b,5.0,5.0a,6.0
Platform : WINDOWS
Issue type : kbprb