OVERLAY

Replaces part of a string with another string and returns the new string value as a VARCHAR.

Behavior type

Immutable if using OCTETS, Stable otherwise

Syntax

OVERLAY ( input‑string PLACING replace‑string FROM position [ FOR extent ] [ USING { CHARACTERS | OCTETS } ] )

Arguments

input‑string

The string to process, of type CHAR or VARCHAR.

replace‑string

The string to replace the specified substring of input‑string, of type CHAR or VARCHAR.

position

Integer ≥1 that specifies the first character or octet of input‑string to overlay replace‑string.

extent

Integer that specifies how many characters or octets of input‑string to overlay with replace‑string. If omitted, OVERLAY uses the length of replace‑string.

For example, compare the following calls to OVERLAY:

OVERLAY omits FOR clause. The number of characters replaced in the input string equals the number of characters in replacement string ABC:
```
dbadmin=> SELECT OVERLAY ('123456789' PLACING 'ABC' FROM 5);
  overlay
-----------
 1234ABC89
(1 row)
```
OVERLAY includes a FOR clause that specifies to replace four characters in the input string with the replacement string. The replacement string is three characters long, so OVERLAY returns a string that is one character shorter than the input string:
```
=> SELECT OVERLAY ('123456789' PLACING 'ABC' FROM 5 FOR 4);
 overlay
----------
 1234ABC9
(1 row)
```
OVERLAY includes a FOR clause that specifies to replace -2 characters in the input string with the replacement string. The function returns a string that is two characters longer than the input string:
```
=> SELECT OVERLAY ('123456789' PLACING 'ABC' FROM 5 FOR -2);
    overlay
----------------
 1234ABC3456789
(1 row)
```

USING CHARACTERS | OCTETS

Specifies whether OVERLAY uses characters (default) or octets.

Note

If you specify USING OCTETS, Vertica calls the OVERLAYB function.

Examples

=> SELECT OVERLAY('123456789' PLACING 'xxx' FROM 2);
  overlay
-----------
 1xxx56789
(1 row)

=> SELECT OVERLAY('123456789' PLACING 'XXX' FROM 2 USING OCTETS);
 overlayb
-----------
 1XXX56789
(1 row)

=> SELECT OVERLAY('123456789' PLACING 'xxx' FROM 2 FOR 4);
 overlay
----------
 1xxx6789
(1 row)

=> SELECT OVERLAY('123456789' PLACING 'xxx' FROM 2 FOR 5);
 overlay
---------
 1xxx789
(1 row)

=> SELECT OVERLAY('123456789' PLACING 'xxx' FROM 2 FOR 6);
 overlay
---------
 1xxx89
(1 row)