Concatenating means to combine two strings together.

This simple example joins the first and second string of words supplied to become a compound word.

Example 9-15. Concatenating Text

   CREATE FUNCTION compound_word(text, text) RETURNS text AS'
     DECLARE
       -- defines an alias name for the two input values
       word1 ALIAS FOR $1;
       word2 ALIAS FOR $2;
     BEGIN
       -- displays the resulting joined words
       RETURN word1 || word2;
     END;
  ' LANGUAGE 'plpgsql';
   

When the words break and fast are passed as arguments to the compound_word() function, it displays:

 SELECT compound_word('break', 'fast');

 compound_word
---------------
 breakfast
(1 row)
      

Note Dealing with Text in PostgreSQL
 

When the words break and fast are supplied to the function, they are inside of single quotes because the function takes a text argument. You will recieve an error if any text string is passed without the single quotes.