MySQL存儲過程是一種自定義的程序,它由一組SQL語句構成,類似于一個函數,可以接收參數,執行一定的操作,最終返回一個結果。在數據字典中,我們可以使用存儲過程來生成和更新數據字典。
首先,我們需要定義一個存儲過程,來生成數據字典的表結構。該存儲過程可以接收一個參數,用于指定需要生成數據字典的數據庫。
DELIMITER $$ CREATE PROCEDURE create_dictionary(IN dbName varchar(50)) BEGIN DECLARE tableName varchar(50); DECLARE columnNum int; DECLARE i int DEFAULT 1; DECLARE sqlstr varchar(2000) DEFAULT ""; SELECT table_name INTO tableName FROM information_schema.tables WHERE table_schema=dbName AND table_name!='dictionary'; SELECT count(*) INTO columnNum FROM information_schema.columns WHERE table_schema=dbName AND table_name=tableName; SET sqlstr = CONCAT('CREATE TABLE dictionary (', '`id` int(11) NOT NULL AUTO_INCREMENT,', '`table_name` varchar(100) NOT NULL,'); WHILE i<= columnNum DO SELECT column_name INTO sqlstr FROM information_schema.columns WHERE table_name=tableName AND table_schema=dbName AND ordinal_position = i; SET sqlstr = CONCAT(sqlstr, '', sqlstr, '`', sqlstr, '` varchar(100) NOT NULL DEFAULT \'\','); SET i = i + 1; END WHILE; SET sqlstr = CONCAT(sqlstr, 'PRIMARY KEY (`id`)) ENGINE=InnoDB DEFAULT CHARSET=utf8;'); PREPARE stmt FROM sqlstr; EXECUTE stmt; DEALLOCATE PREPARE stmt; END $$ DELIMITER ;
該存儲過程的作用是根據指定的數據庫名,查找其中表的信息,生成對應的數據字典表結構。接下來,我們還需要編寫一個存儲過程,用于更新數據字典中的信息。該存儲過程需要接收兩個參數,一個是需要更新的表名,一個是需要更新的字段名。
DELIMITER $$ CREATE PROCEDURE update_dictionary(IN dbName varchar(50), IN tableName varchar(50)) BEGIN DECLARE columnName varchar(50); DECLARE sqlstr varchar(2000) DEFAULT ""; SELECT column_name INTO columnName FROM information_schema.columns WHERE table_schema=dbName AND table_name=tableName AND ordinal_position=1; SET sqlstr = CONCAT('REPLACE INTO dictionary(`table_name`, `', '', columnName, '') VALUES("', tableName, '", "'); SELECT GROUP_CONCAT(CONCAT(column_name, ':"', column_type, ',', IS_NULLABLE, ',', COLUMN_KEY) SEPARATOR ' ' ) INTO sqlstr FROM information_schema.columns WHERE table_schema=dbName AND table_name=tableName AND ordinal_position >1; SET sqlstr = CONCAT(sqlstr, '");'); PREPARE stmt FROM sqlstr; EXECUTE stmt; DEALLOCATE PREPARE stmt; END $$ DELIMITER ;
以上是使用MySQL存儲過程來實現數據字典的一些基本操作,我們可以根據自己的需要進行調整和改進。