Year: 2018
Date: 4-24
concat
1. Function: Concatenate multiple strings into one string.
2. Syntax: concat(str1, str2,...)
The return result is the string generated by the connection parameters. If any parameter is null, the return value is null
Date: 4-22
1
In the mysql database, add a column to the table
ALTER TABLE talbe_name
ADD COLUMN column_name column_type NULL COMMENT 'column_comment' AFTER `table_old_column`,
illustrate:
table_name The name of the table to be added
column_name New column name
column_type new column type
column_comment New column description
table_old_column: the original column in the table / [suggestion: the new column is after the last column in the original table]
2
Table, modify a column [demo description: modify the comment of a field in the table]
ALTER TABLE table_name
MODIFY COLUMN update_column_name VARCHAR(64) NULL COMMENT 'update_comment' AFTER `table_old_column` ;
illustrate:
table_name: table name
update_column_name : the name of the column to modify
VARCHAR(64) is the original type of the original field, if necessary, you can modify it to the field type you need
update_commenet: the newly modified comment