Here is a sample query:
UPDATE `table1`
SET `table1`.`field1` = (SELECT COUNT(*)
FROM `table2`
WHERE `table2`.`field2` = `table1`.`fie开发者_StackOverflowld2`)
MySQL gives me an error message that table1
.field2
does not found.
Please advice
I think it's easier to understand with a less abstract example.
materials
table
CREATE TABLE IF NOT EXISTS `materials` (
`material_id` int(11) NOT NULL auto_increment,
`name` varchar(20) NOT NULL,
`qty` tinyint(4) default NULL,
PRIMARY KEY (`material_id`)
)
part_materials
table
CREATE TABLE IF NOT EXISTS `parts` (
`part_id` int(11) NOT NULL auto_increment,
`material_id` varchar(30) NOT NULL,
PRIMARY KEY (`part_id`,`material_id`)
)
To update materials.qty with number of parts using that material:
update materials set qty=(select count(*) from part_materials where material_id=materials.material_id)
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