Cast int to varchar

Question

I have below query and need to cast id to varchar

Schema

create table t9 (id int, name varchar (55));
insert into t9( id, name)values(2, 'bob');

What I tried

select CAST(id as VARCHAR(50)) as col1 from t9;

select CONVERT(VARCHAR(50),id) as colI1 from t9;

but they don't work. Please suggest.

Answer 1

You will need to cast or convert as a CHAR datatype, there is no varchar datatype that you can cast/convert data to:

select CAST(id as CHAR(50)) as col1 
from t9;

select CONVERT(id, CHAR(50)) as colI1 
from t9;

See the following SQL — in action — over at SQL Fiddle :

/*! Build Schema */
create table t9 (id INT, name VARCHAR(55));
insert into t9 (id, name) values (2, 'bob');

/*! SQL Queries */
select CAST(id as CHAR(50)) as col1 from t9;
select CONVERT(id, CHAR(50)) as colI1 from t9;

Besides the fact that you were trying to convert to an incorrect datatype, the syntax that you were using for convert was incorrect. The convert function uses the following where expr is your column or value:

 CONVERT(expr,type)

or

 CONVERT(expr USING transcoding_name)

Your original query had the syntax backwards.

Answer 2

You're getting that because VARCHAR is not a valid type to cast into. According to the MySQL docs ( http://dev.mysql.com/doc/refman/5.5/en/cast-functions.html#function_cast ) you can only cast to:

• BINARY[(N)]
• CHAR[(N)]
• DATE
• DATETIME
• DECIMAL[(M[,D])]
• SIGNED
• [INTEGER]
• TIME
• UNSIGNED [INTEGER]

I think your best-bet is to use CHAR .

Answer 3

Yes

SELECT id || '' FROM some_table;
or SELECT id::text FROM some_table;

is postgresql, but mySql doesn't allow that!

short cut in mySql:

SELECT concat(id, '') FROM some_table;

Answer 4

I don't have MySQL, but there are RDBMS (Postgres, among others) in which you can use the hack

SELECT id || '' FROM some_table;

The concatenate does an implicit conversion.

Answer 5

我解决了将整数列 xa varchar列与

where CAST(Column_name AS CHAR CHARACTER SET latin1 ) collate latin1_general_ci = varchar_column_name

Answer 6

采用 ：

SELECT cast(CHAR(50),id) as colI1 from t9;

Answer 7

I will be answering this in general terms, and very thankful to the above contributers.
I am using MySQL on MySQL Workbench. I had a similar issue trying to concatenate a char and an int together using the GROUP_CONCAT method. In summary, what has worked for me is this:

let's say your char is 'c' and int is 'i', so, the query becomes:
...GROUP_CONCAT(CONCAT(c,' ', CAST(i AS CHAR))...

Answer 8

Should be able to do something like this also:

Select (id :> VARCHAR(10)) as converted__id_int
from t9