Database table table
New field json
how can I tell if the json field exists? If it does not exist, create a field json in varchar format
because the code is common to many programs. Some databases already have the json field, and some do not.. How to judge when inserting.
there is a COLUMNS table in MySQL's information_schema library that records the field information of all tables in all mysql libraries. So check whether there is a json field in each table directly according to the information of this table, and then create it.
IF NOT EXISTS( SELECT NULL
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = 'tablename'
AND table_schema = 'db_name'
AND column_name = 'json') THEN
ALTER TABLE `TableName` ADD `json` VARCHAR(255) NOT NULL;
END IF;IF NOT EXISTS(SELECT 1 FROM information_schema.COLUMNS WHERE TABLE_SCHEMA='()' AND table_name='table' AND COLUMN_NAME='json') THEN
ALTER TABLE `table` ADD `json` VARCHAR(255) NOT NULL;
END IF;do a check-in function `create_time` decimal(20,3) NOT NULL, `create_date_ymd` varchar(15) NOT NULL COMMENT , `create_date_ym` varchar(15) NOT NULL, `create_date_y` int(4) NOT NULL, `create_date_m` int(2) NOT NULL, `create_date_d` int(2) ...
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