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F_PRED

• function from adhoc

U_PRED

• function from adhoc
• Input VARCHAR(1) Character, INTEGER Amount of characters before the character in ASCII-Table
• Output VARCHAR(1) n-predecessor of character from parameter 1

If parameter 2 equal to 512 (or multiple of 512) the return is the same as the input.

Both functions ignore UTF8 chars

Example

 SELECT 'b' AS ISCORRECT, F_PRED('a', -1) FROM RDB$DATABASE;

Expected results:

 ISCORRECT F_PRED
 ========= ======
 b         b

Example

 SELECT 'a' AS ISCORRECT, F_PRED('b', 1) FROM RDB$DATABASE;

Expected results:

 ISCORRECT F_PRED
 ========= ======
 a         a

Example

 SELECT NULL AS ISCORRECT, F_PRED(NULL, NULL) FROM RDB$DATABASE;

Expected results:

 ISCORRECT F_PRED
 ========= ======
 <null>    <null>                  

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