Created table with generated columns throw an error - mysql

Question

I am trying to build my table in MySQL following this answer. Hower i keep getting errors in MySQL even launching the same query used as example in the answer
this query is from documentation and works correctly
CREATE TABLE triangle (
sidea DOUBLE,
sideb DOUBLE,
sidec DOUBLE AS (SQRT(sidea * sidea + sideb * sideb)) stored
);
this query comes from the answer i've linked and it gives me an error
CREATE TABLE IF NOT EXISTS MyTable (
id int NOT NULL AUTO_INCREMENT,
name varchar(50) NOT NULL,
description varchar(50) NOT NULL,
slug text NOT NULL AS (SHA2(CONCAT(name, description), 256) STORED,
PRIMARY KEY (id)
) DEFAULT CHARSET=utf8;
this is the query i am trying to execute based on the answer which is giving me also an error
CREATE TABLE IF NOT EXISTS myTable(
id BIGINT NOT NULL AUTO_INCREMENT,
first VARCHAR(104) NOT NULL DEFAULT '',
second DATETIME NULL,
third DATETIME NULL,
fourth VARCHAR(255) NULL,
table_key varchar(64) NOT NULL AS (SHA2(concat_ws(',',first, second, third, fourth), 256)) stored unique,
PRIMARY KEY (id),
INDEX (first));
can you help me figuring out why it's not working?
Note that SHA2(concat_ws(',',first, second, third, fourth), 256) this works in a normal select statement
EDIT
this is the error i am getting
Query execution failed
Reason:
Errore SQL [1064] [42000]: (conn:28) You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'AS (SHA2(CONCAT(name, description), 256) STORED,
PRIMARY KEY (id)
) DEFAULT ' at line 5
Query is : CREATE TABLE IF NOT EXISTS MyTable (
id int NOT NULL AUTO_INCREMENT,
name varchar(50) NOT NULL,
description varchar(50) NOT NULL,
slug text NOT NULL AS (SHA2(CONCAT(name, description), 256) STORED,
PRIMARY KEY (id)
) DEFAULT CHARSET=utf8

Answer 1

You have to add the NOT NULL after the AS part (computed column definition) of the column like this:
CREATE TABLE IF NOT EXISTS myTable(
id BIGINT NOT NULL AUTO_INCREMENT,
first VARCHAR(104) NOT NULL DEFAULT '',
second DATETIME NULL,
third DATETIME NULL,
fourth VARCHAR(255) NULL,
table_key varchar(64) AS (SHA2(concat_ws(',',first, second, third, fourth), 256)) stored unique NOT NULL,
PRIMARY KEY (id),
INDEX (first)
);
Also have a look at the official document of CREATE TABLE. There you can find the description of the datatype syntax. The definition of the computed column is part of the datatype.