Hi Carsten,
On 04/22/11 22:11, Carsten Pedersen wrote:
On 22.04.2011 21:37, Daniel Kraft wrote:
DROP DATABASE `test`;
CREATE DATABASE `test`;
USE `test`;
CREATE TABLE `mytable`
(`ID` SERIAL,
`Type` INTEGER UNSIGNED NULL,
PRIMARY KEY (`ID`));
INSERT INTO `mytable` (`Type`) VALUES (NULL);
CREATE TABLE `types`
(`ID` SERIAL,
`Name` TEXT NOT NULL,
PRIMARY KEY (`ID`));
INSERT INTO `types` (`Name`) VALUES ('Type A'), ('Type B');
DELIMITER |
CREATE FUNCTION `EMPTY_STRING` (value TEXT)
RETURNS TEXT
DETERMINISTIC
BEGIN
RETURN IF(value IS NULL, '', value);
END|
DELIMITER ;
CREATE VIEW `myview` AS
SELECT a.*, EMPTY_STRING(b.`Name`) AS `TypeName`
FROM `mytable` a
LEFT JOIN `types` b ON a.`Type` = b.`ID`;
SELECT COUNT(*) FROM `myview` WHERE `TypeName` IS NULL;
SELECT COUNT(*) FROM `myview` WHERE `TypeName` IS NOT NULL;
SELECT COUNT(*) FROM `myview` WHERE `TypeName` LIKE '%';
(I tried to simplify my problem as far as possible.) When I run this
against MySQL 5.0.24a, I get three times "0" as output from the SELECTs
at the end -- shouldn't at least one of them match the single row?
(Preferably first and third ones.)
What am I doing wrong here? I have no clue what's going on... Thanks a
lot!
Hint: What's the output of "SELECT * FROM `myview`?
I get:
mysql> select * from myview;
+----+------+----------+
| ID | Type | TypeName |
+----+------+----------+
| 1 | NULL | |
+----+------+----------+
1 row in set (0.00 sec)
mysql> select *, `TypeName` IS NOT NULL from myview;
+----+------+----------+------------------------+
| ID | Type | TypeName | `TypeName` IS NOT NULL |
+----+------+----------+------------------------+
| 1 | NULL | | 1 |
+----+------+----------+------------------------+
1 row in set (0.00 sec)
Should this tell me something? To me, it looks as expected and fine.
Cheers,
Daniel
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