根据 SQL 中另一个表中的值从列中提取子字符串

Question

In SQL (let's assume ANSI standard SQL), is it possible to extract a substring from one column, based on another table, and put this substring into another column?

Example, from the following tables:

VISITS
name       summary
---------------------------------------------
john       visit to London
jack       hotel in Paris with park visits
joe        b&b in Paris with ice cream
james      holidays in London and museums
jason      visit in Milan and fashion tour

LOCATIONS
id    name
-------------
1     Paris
2     London
3     Milan
4     Berlin

The idea is to extract the location from the summary column and output the following:

VISITS
name       summary                              location
---------------------------------------------
john       visit to London                      London
jack       hotel in Paris with park visits      Paris
joe        b&b in Paris with ice cream          Paris
james      holidays in London and museums       London
jason      visit in Milan and fashion tour      Milan

Answer 1

You can do pattern matching:

select v.*, l.name
from visits v
left join locations l on v.summary like concat('%', l.name, '%')

As commented by jarlh ANSI sql has operator || for string concatenation, so, depending on your database:

select v.*, l.name
from visits v
left join locations l on v.summary like '%' || l.name || '%'