SQLite3: Find match of a certain part of column value by regular expression and replace it with another value. - sql

Question

I'm an absolute beginner at SQL. I do know how to use SQL commands that belong to Data Manipulation Language and Data Definition Language.
The name of the table is ways_tags
id,key,value,type
164931009,street,6th Main Road Ram Nagar (N) Extn,addr
The header represents the column names, I've printed just one row.
Here's what I want to accomplish:
Select observations that have type as addr and key as street.
In such observations, scan the characters of value column and check if the last 4 characters match Extn and replace it with Extension
Also, is there a way I can reduce size of the code, where it checks for TWO patterns instead of ONE?
In other words
You can replace what I'd like to accomplish on 2. with something like
In such observations, scan the characters of value column:
i. If last 4 characters in the value column is Extn replace with Extension.
ii.If last 2 characters in the value column is St. replace with Street.
I'm really sorry, but I just know the pseudocode and don't know how to incorporate regular expressions with normal SQL, and so I can't post anything to show that I've tried.
So eventually after performing the step,
164931009,street,6th Main Road Ram Nagar (N) Extension,addr
is the updated observation instead of
164931009,street,6th Main Road Ram Nagar (N) Extn,addr

Answer 1

Select observations that have type as addr and key as street.
… scan the characters of value column and check if the last 4 characters match Extn
WHERE type = 'addr'
AND key = 'street'
AND value LIKE '%Extn'
… and replace it with Extension
If "Extn" does not occur anywhere else in the value, this could be done with replace(), but in the general case, you have to extract all but the four last characters, and append the new value:
substr(value, 1, length(value) - 4) || 'Extension'
Then plug this into an UPDATE statement:
UPDATE ways_tags
SET value = substr(value, 1, length(value) - 4) || 'Extension'
WHERE type = 'addr'
AND key = 'street'
AND value LIKE '%Extn';
Doing two replacements in a single statement would be possible with a CASE expression, but would not reduce code size.