MySQL Custom function call does not produce results

Code for custom functions:

drop FUNCTION IF EXISTS fn_hrstaffbase_getnamefromidcard
Delimiter//
CREATE FUNCTION Fn_hrstaffbase_getnamefromidcard (a VARCHAR ())
RETURNS VARCHAR ()
Begin
Return (SELECT staff_ name   from hr_staff_base where idcard = a);
END//

-- ------------------------------------------------------------------------------------------------------------- --------

Function call Query:

Select Fn_hrstaffbase_getnamefromidcard (' 299012234225 ')

-- ------------------------------------------------------------------------------

It's all null,

Processing method:

When you create a new library, you must

You can also modify the database settings: Right-click the database, mouse to edit the database

To set up a database such as:

The original settings are:

The database can read only Latin values and cannot read Chinese

So the result of calling the function is:

-- ---------------------------------------------------------------

After you modify the database settings, the query results appear:

#################################################################################

Sometimes MySQL cannot build a custom function because the function 2 is not turned on

Enter show variables like '%func% '; Command

You will see the state of the log_bin_trust_function_creators, if it is off, the function of the custom function is closed

Input command set global Log_bin_trust_function_creators=1;

Log_bin_trust_function_creators can be turned on with custom function functions

However, this setting is a temporary scenario because the status will turn off after MySQL automatically restarts, so you need to

Add the "--log-bin-trust-function-creators=1" parameter when the service starts. Or add Log-bin-trust-function-creators=1 in the [mysqld] section of My.ini (MY.CNF).

MySQL Custom function call does not produce results