Creating a User Defined Function using a C program

You can create a User Defined Function (UDF) function using a C program and install it on the Teradata database in order to use regular expressions.

Before you begin

Retrieve the Regex_INSTR.c file from the Downloads tab in the left panel of this page.

Procedure

Create a C program like Regex_INSTR.c.
Put this C file on your Teradata database.
Login to Teradata using the user created previously.

Create a UDF function. You can use the following command for example:

CREATE FUNCTION Regex_INSTR (
InputString VARCHAR(4096) CHARACTER SET LATIN,
PatternString VARCHAR(512) CHARACTER SET LATIN )
RETURNS INTEGER
LANGUAGE C
NO SQL
EXTERNAL NAME 'CS!Regex_INSTR!/Regex_INSTR.c!F!Regex_INSTR1'
PARAMETER STYLE SQL;

Test the UDF using the following SQL instruction:
```
select Regex_INSTR('A','[A-Z]');
```
The instruction should return 1.

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