The column will be defined as a varchar(25) data type that allows NULL values. This MariaDB ALTER TABLE example will rename the column called host_name to hname. Let's look at an example that shows how to rename a column in a MariaDB table using the ALTER TABLE statement. It tells MariaDB where in the table to position the column, if you wish to change its position. You must specify the column definition when renaming the column, even if it does not change. column_definition The datatype and definition of the column (NULL or NOT NULL, etc). table_name The name of the table to modify. The syntax to rename a column in a table in MariaDB (using the ALTER TABLE statement) is: ALTER TABLE table_name The server_name column will be modified to a varchar(30) NOT NULL column (and will not change position in the websites table definition, as there is no FIRST | AFTER specified). The host_name field will be changed to a varchar(45) column that allows NULL values and will appear after the website_id column in the table. This ALTER TABLE example will modify two columns to the websites table - host_name and server_name. Let's look at an example that shows how to modify multiple columns in a MariaDB table using the ALTER TABLE statement. column_definition The modified datatype and definition of the column (NULL or NOT NULL, etc). column_name The name of the column to modify in the table. The syntax to modify multiple columns in a table in MariaDB (using the ALTER TABLE statement) is: ALTER TABLE table_name The creation_date column will be created as a date column and will appear at the end of the table. ![]() The host_name field will be created as a varchar(20) column that allows NULL values and will appear after the server_name column in the table. This ALTER TABLE example will add two columns to the websites table - host_name and creation_date. Let's look at an example that shows how to add multiple columns in a MariaDB table using the ALTER TABLE statement. On the File menu, select Save table name. Under Column Name, select the name you want to change and type a new one. If this parameter is not specified, the new column will be added to the end of the table. Rename a column using table designer In Object Explorer, right-click the table to which you want to rename columns and choose Design. It tells MariaDB where in the table to create the column. new_column_name The name of the new column to add to the table. (I'm not a MySQL guru, feel free to correct me.The syntax to add multiple columns in a table in MariaDB (using the ALTER TABLE statement) is: ALTER TABLE table_name Furthermore, the first one is much easier to read. ![]() ![]() If I'm right the second version runs the complex (maybe bottleneck) subquery on table test2 twice, so it should be slower than the first query which runs the complex subquery only once. | 2 | SUBQUERY | test2 | ALL | NULL | NULL | NULL | NULL | 3 | 100.00 | | | 1 | PRIMARY | test | ALL | NULL | NULL | NULL | NULL | 3 | 100.00 | | ((SELECT SUM(s) FROM test2) + (a + b)) / (a -b) as z ![]() For a complete reference of all the data types available in MySQL, go to our complete Data Types reference. The data type specifies what type of data the column can hold. ADD DateOfBirth date Notice that the new column, 'DateOfBirth', is of type date and is going to hold a date. | 3 | SUBQUERY | test2 | ALL | NULL | NULL | NULL | NULL | 3 | 100.00 | | We use the following SQL statement: Example. | 2 | DERIVED | test | ALL | NULL | NULL | NULL | NULL | 3 | 100.00 | | | 1 | PRIMARY | | ALL | NULL | NULL | NULL | NULL | 3 | 100.00 | | | id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra | Here are the two queries and their explain results: explain extended SELECT
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