How to replace a part of string in char or varchar column?


If you use Firebird 2.1 or above, you can use built-in REPLACE function:

update t1 set c1 = replace(c1, 'old_str', 'new_str');

More info can be found in Firebird manual:

http://www.firebirdsql.org/refdocs/langrefupd21-intfunc-replace.html

If you are using older version of Firebird, you can combine STRPOS and SUBSTRING function and concatenate parts before and after the search string. Here's how the statement might look like:

update t1 set c1 =
CASE when strpos('old_str', c1) = 0 then c1
ELSE
substring(c1 from 1 for strpos('old_str', c1) - 1)
||'new_str'
||substring(c1 from strpos('old_str', c1)+char_length('new_str'))
END

Note that CHAR_LENGTH is available since Firebird 2.0. If you use earlier versions, try using STRLEN UDF instead.

Another useful function for string replacement is OVERLAY, also introduced in version 2.1. It also replaces the characters, main difference being replacing by position (and optionally length) instead of string-to-string replacement. The syntax is:

OVERLAY (string PLACING replacement-string FROM position [FOR length])

If replacement string would stretch over the end of the original string, the result would be extended. For example:

OVERLAY ('abc' PLACING 'de' FROM 3)

would result in string 'abde'.

The Length parameter is optional and used to limit the number of characters taken from replacement-string.


Do you find this FAQ incorrect or incomplete? Please e-mail us what needs to be changed. To ensure quality, each change is checked by our editors (and often tested on live Firebird databases), before it enters the main FAQ database. If you desire so, the changes will be credited to your name. To learn more, visit our add content page.

If you are a commercial tool maker and your tool features a great way to handle the issue written about in this FAQ, please check out our advertisement page.



All contents are copyright © 2007-2017 FirebirdFAQ.org unless otherwise stated in the text.


Links   Firebird   News   FlameRobin   Home Inventory powered by FB  
Add content   Advertise   About  

Categories
 Newbies
 SQL
 Installation and setup
 Backup and restore
 Performance
 Security
 Connectivity and API
 HOWTOs
 Errors and error codes
 Miscellaneous