MySql question de syntaxe

Question

Pourquoi ce travail parfaitement:

SET @columnQuery = 'INSERT INTO ColumnNames SELECT ORDINAL_POSITION, COLUMN_NAME FROM information_schema.columns WHERE TABLE_NAME=''residents'' ORDER BY ORDINAL_POSITION;'; 

PREPARE STMT FROM @columnQuery; 
EXECUTE STMT; 

mais cela ne fait pas:

DECLARE TableName VARCHAR(50); 
SET @TableName = 'residents'; 

SET @columnQuery = 'INSERT INTO ColumnNames SELECT ORDINAL_POSITION, COLUMN_NAME FROM information_schema.columns WHERE TABLE_NAME=''' + @TableName + ''' ORDER BY ORDINAL_POSITION;'; 

PREPARE STMT FROM @columnQuery; 
EXECUTE STMT; 

et ne le fait:

DECLARE TableName VARCHAR(50); 
SET @TableName = 'residents'; 

SET @columnQuery = CONCAT('INSERT INTO ColumnNames SELECT ORDINAL_POSITION, COLUMN_NAME FROM information_schema.columns WHERE TABLE_NAME=''', @TableName, ''' ORDER BY ORDINAL_POSITION;'); 

PREPARE STMT FROM @columnQuery; 
EXECUTE STMT; 

Ni le fait:

SET @columnQuery = 'INSERT INTO ColumnNames SELECT ORDINAL_POSITION, COLUMN_NAME FROM information_schema.columns WHERE TABLE_NAME=? ORDER BY ORDINAL_POSITION;'; 

PREPARE STMT FROM @columnQuery; 
EXECUTE STMT USING @TableName; 

Voici la partie du sproc qui me donne des problèmes:

CREATE PROCEDURE sp_ReturnSingleRowAsXml 
(
    IN TableName VARCHAR(50) 
) 
BEGIN 

DECLARE columnQuery VARCHAR(1000); 

DROP TABLE IF EXISTS ColumnNames; 

CREATE TEMPORARY TABLE ColumnNames (
    ID INT, ColumnName VARCHAR(50) 
); 

SET @columnQuery = 'INSERT INTO ColumnNames SELECT ORDINAL_POSITION, COLUMN_NAME FROM information_schema.columns WHERE TABLE_NAME=''' + @TableName + ''' ORDER BY ORDINAL_POSITION;'; 

PREPARE STMT FROM @columnQuery; 
EXECUTE STMT; 

select * from ColumnNames; 

END; 

CALL sp_ReturnSingleRowAsXml('residents'); 

Le select retourne rien quand il devrait revenir à environ 40 lignes. MAIS, si je code dur le mot «résidents» dans la @columnQuery, j'obtiens des résultats! Et oui, il y a certainement une table nommée 'résidents'.

Parfois, je reçois cette erreur, parfois non, selon que j'utilise CONCAT ou tout simplement des chaînes manuellement: concaténer

MySQL Database Erreur: Vous avez une erreur dans votre syntaxe SQL; consultez le manuel qui correspond à votre version du serveur MySQL pour la bonne syntaxe à utiliser près « NULL » à la ligne 1

Answer 1

j'ai pu obtenir de travailler avec les éléments suivants:

CREATE PROCEDURE `sp_ReturnSingleRowAsXml`( 
    IN TableName VARCHAR(50) 
) 
BEGIN 

DROP TABLE IF EXISTS ColumnNames; 

CREATE TEMPORARY TABLE ColumnNames ( 
    ID INT, ColumnName VARCHAR(50) 
); 
SET @tblName = TableName; 
SET @columnQuery = 'INSERT INTO ColumnNames SELECT ORDINAL_POSITION, COLUMN_NAME FROM information_schema.columns WHERE TABLE_NAME=? ORDER BY ORDINAL_POSITION;'; 

PREPARE STMT FROM @columnQuery; 
EXECUTE STMT USING @tblName; 

select * from ColumnNames; 

END 

Answer 2

essayez ceci:

DECLARE TableName VARCHAR(50); 
SET @TableName = 'residents'; 

SET @columnQuery = 'INSERT INTO ColumnNames SELECT ORDINAL_POSITION, COLUMN_NAME FROM information_schema.columns WHERE TABLE_NAME=? ORDER BY ORDINAL_POSITION;'; 

PREPARE STMT FROM @columnQuery; 
EXECUTE STMT USING @TableName;