Creating ENUM variable type in MySQL

Question

I am using an ENUM data type in MySQL and would like to reuse it, but not retype in the values. Is there an equivalent to the C, C++ way of defining types in MySQL?

I would like to do the following:

DEFINE ETYPE ENUM('a','b','c','d'); CREATE TABLE Table_1 (item1 ETYPE, item2 ETYPE); 

Is this possible?

Thanks

Answer 1

No. MySQL does not support CREATE DOMAIN or CREATE TYPE as, for example, PostgreSQL does.

You'll probably have to enter all the names again. You can mitigate the work it takes to do this by using copy & paste, or SQL scripts.

You could also use the INFORMATION_SCHEMA tables to get the text of the ENUM definition, and then interpolate that into a new CREATE TABLE statement.

You can also use CREATE TABLE AS in creative ways to copy a type definition. Here's a demonstration:

CREATE TABLE foo ( f ENUM('abc', 'xyz') ); CREATE TABLE bar AS SELECT f AS b FROM foo; SHOW CREATE TABLE bar; 

Outputs:

CREATE TABLE `bar` (   `b` enum('abc','xyz') default NULL )  

Finally, I suggest that if your ENUM has many values in it (which I'm guessing is true since you're looking for a solution to avoid typing them), you should probably be using a lookup table instead of the ENUM data type.

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Re comment from @bliako:

You can do what you describe this way:

CREATE TABLE bar (pop INT NOT NULL, name VARCHAR(100)) AS SELECT 0 AS pop, NULL AS name, f FROM foo; 

I tried this on MySQL 5.7.27, and it worked.

It's interesting to note that you don't have to declare all three columns in the CREATE TABLE line. The third column f will be added automatically.

It's also interesting that I had to give column aliases in the SELECT statement to make sure the column names match those declared in the CREATE TABLE. Otherwise if the column names don't match, you end up with extra columns, and their data types are not what you expect:

create table bar (pop int not null, name varchar(100))  as select 0 as c1, null as c2, f from foo;  show create table bar\G  CREATE TABLE `bar` (   `pop` int(11) NOT NULL,   `name` varchar(100) DEFAULT NULL,   `c1` binary(0) DEFAULT NULL,   `c2` binary(0) DEFAULT NULL,   `f` enum('abc','xyz') DEFAULT NULL )