Hi,
thanks for the fast reply!
On 04/22/11 21:39, Daevid Vincent 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!
>
> Try this maybe:
>
> SELECT COUNT(*) FROM `myview` HAVING `TypeName` IS NULL;
> SELECT COUNT(*) FROM `myview` HAVING `TypeName` IS NOT NULL;
> SELECT COUNT(*) FROM `myview` HAVING `TypeName` LIKE '%';
When I try those, I get:
ERROR 1054 (42S22) at line 35: Unknown column 'TypeName' in 'having clause'
What would be the difference? (I've never used HAVING before.)
Yours,
Daniel
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