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POWhat's with "id_" and "id" and "id" causes the Error 1005: Can't create table 'xxx.xxx' (errno: 121)
 

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  1. POWhat's with "id_" and "id" and "id" causes the Error 1005: Can't create table 'xxx.xxx' (errno: 121)
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    <p>I am new to MySQL and was creating a complex EER diagram. After creation, I "Forward Engineer..." the model and hit the dreaded ERROR: Error 1005: Can't create table 'xxx.xxx' (errno: 121). I created another simplified model of two tables with a 1:M relationship, but used "id_" for the primary and foreign key names. That worked. </p> <pre><code>i.e. TABLE_A id_TABLE_A INT TABLE_B id_TABLE_B INT id_TABLE_A INT </code></pre> <p>where, there is a one to many relationship between TABLE_A [1]--&lt;[M] TABLE_B, and TABLE_B.id_TABLE_A is the foreign key</p> <p>Looking at my complex EER diagram, I noticed I used "id" with no underscore for the primary and foreign key names. I inserted the underscore after "id" and Forward Engineer'ed the model and it worked with no errors. So, here are two simple example models, one with the "id_" and the other with "id". The "id_" DOES NOT cause the Error 1005 and the "id" causes the Error 1005. <strong>Anyone with an idea as to why this anomaly happens with MySQL?</strong></p> <p>=============================================================================== <strong>Good Model:</strong></p> <pre><code>SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0; SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0; SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL'; CREATE SCHEMA IF NOT EXISTS `mydb` DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci ; USE `mydb` ; DROP TABLE IF EXISTS `mydb`.`TABLE_A` ; CREATE TABLE IF NOT EXISTS `mydb`.`TABLE_A` ( `id_TABLE_A` INT NOT NULL AUTO_INCREMENT , PRIMARY KEY (`id_TABLE_A`) , UNIQUE INDEX `id_TABLE_A_UNIQUE` (`id_TABLE_A` ASC) ) ENGINE = InnoDB; DROP TABLE IF EXISTS `mydb`.`TABLE_B` ; CREATE TABLE IF NOT EXISTS `mydb`.`TABLE_B` ( `id_TABLE_B` INT NOT NULL AUTO_INCREMENT , `id_TABLE_A` INT NOT NULL , PRIMARY KEY (`id_TABLE_B`) , UNIQUE INDEX `id_TABLE_B_UNIQUE` (`id_TABLE_B` ASC) , INDEX `id_TABLE_A` (`id_TABLE_A` ASC) , CONSTRAINT `id_TABLE_A` FOREIGN KEY (`id_TABLE_A` ) REFERENCES `mydb`.`TABLE_A` (`id_TABLE_A` ) ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE = InnoDB; SET SQL_MODE=@OLD_SQL_MODE; SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS; SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS; </code></pre> <p><strong>RESULT:</strong></p> <pre><code>Build is successful. </code></pre> <p>===============================================================================</p> <p><strong>Bad Model:</strong></p> <pre><code>SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0; SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0; SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL'; CREATE SCHEMA IF NOT EXISTS `mydb` DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci ; USE `mydb` ; DROP TABLE IF EXISTS `mydb`.`TABLE_A` ; CREATE TABLE IF NOT EXISTS `mydb`.`TABLE_A` ( `idTABLE_A` INT NOT NULL AUTO_INCREMENT , PRIMARY KEY (`idTABLE_A`) , UNIQUE INDEX `idTABLE_A_UNIQUE` (`idTABLE_A` ASC) ) ENGINE = InnoDB; DROP TABLE IF EXISTS `mydb`.`TABLE_B` ; CREATE TABLE IF NOT EXISTS `mydb`.`TABLE_B` ( `idTABLE_B` INT NOT NULL AUTO_INCREMENT , `idTABLE_A` INT NOT NULL , PRIMARY KEY (`idTABLE_B`) , UNIQUE INDEX `idTABLE_B_UNIQUE` (`idTABLE_B` ASC) , INDEX `idTABLE_A` (`idTABLE_A` ASC) , CONSTRAINT `idTABLE_A` FOREIGN KEY (`idTABLE_A` ) REFERENCES `mydb`.`TABLE_A` (`idTABLE_A` ) ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE = InnoDB; SET SQL_MODE=@OLD_SQL_MODE; SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS; SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS; </code></pre> <p><strong>RESULT:</strong></p> <pre><code>Executing SQL script in server ERROR: Error 1005: Can't create table 'mydb.table_b' (errno: 121) CREATE TABLE IF NOT EXISTS `mydb`.`TABLE_B` ( `idTABLE_B` INT NOT NULL AUTO_INCREMENT , `idTABLE_A` INT NOT NULL , PRIMARY KEY (`idTABLE_B`) , UNIQUE INDEX `idTABLE_B_UNIQUE` (`idTABLE_B` ASC) , INDEX `idTABLE_A` (`idTABLE_A` ASC) , CONSTRAINT `idTABLE_A` FOREIGN KEY (`idTABLE_A` ) REFERENCES `mydb`.`TABLE_A` (`idTABLE_A` ) ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE = InnoDB SQL script execution finished: statements: 8 succeeded, 1 failed </code></pre>
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    1. PTQuestion
    1. USOMG Ponies
    1. USRob Hoth
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    1. PO
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      1. PTAnswer
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    1. COWhy are you not enclosing identifiers in backticks?
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      1. POWhat's with "id_" and "id" and "id" causes the Error 1005: Can't create table 'xxx.xxx' (errno: 121)
      1. USLightness Races in Orbit
    2. COi never use backticks - what an utter waste of time and effort unless it's a reserved word or you want spaces in it - so avoid reserved words and spaces - SIMPLE.
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      1. POWhat's with "id_" and "id" and "id" causes the Error 1005: Can't create table 'xxx.xxx' (errno: 121)
      1. USJon Black
 

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