MySQL 变量数据库名称语法错误

Question

我正在尝试为 MySQL 查询设置数据库名称。我已经能够让我的第一个查询正常工作，但第二个查询我正在努力找出我的语法错误在哪里。我猜这与变量有关，但我被困住了。

SET @db = CONCAT('SELECT client_databases.database_name
FROM client_databases
JOIN jobs ON jobs.organisation_id = client_databases.organisation_id
WHERE jobs.transaction_reference="K01-REC0000001"');

SET @q = CONCAT('SELECT receipts_lines.id, product_code, product_name, receipts_lines.is_putaway
    FROM ', @db ,'.receipts
    JOIN ', @db ,'.receipts_lines ON receipts_lines.receipt_id = receipts.id
    WHERE reference_number="K01-REC0000001"');

PREPARE stmt FROM @q;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

Answer 1

你应该做这样的事情。您在 @db 中选择数据库名称并使用它来构建您的 stmt

SELECT client_databases.database_name INTO @db
FROM client_databases
JOIN jobs ON jobs.organisation_id = client_databases.organisation_id
WHERE jobs.transaction_reference="K01-REC0000001";

SET @q = CONCAT('SELECT receipts_lines.id, product_code, product_name, receipts_lines.is_putaway
    FROM ', @db ,'.receipts
    JOIN ', @db ,'.receipts_lines ON receipts_lines.receipt_id = receipts.id
    WHERE reference_number="K01-REC0000001"');

PREPARE stmt FROM @q;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;