检查 CASE 表达式中的多个条件 SQL

Question

I am trying to parse a free form text with a case expression and I am not able to get the results I am expecting. Can you please suggest if I can achieve this in SQL?

Here I have shown some sample data in the SQL Fiddle link below, but the city_lookup table has 100s of rows because there are multiple cities in a state. The case statement was just an attempt to put them in appropriate buckets. The free form text can contain multiple keywords which can contain cities from the lookup table(city_lookup) and for every such occurrence, we need to record the visited state of the user. For example if the freeform text contains two cities, I should be able to write the output as two different rows with each city visited, for the same user.

SQL Fiddle Link - http://sqlfiddle.com/#!7/61ef9

DDL

create table city_lookup(city varchar(50), state varchar(50));
insert into city_lookup values('dallas', 'texas');
insert into city_lookup values('austin', 'texas');
insert into city_lookup values('phoenix', 'arizona');
insert into city_lookup values('tuscon', 'arizona');
insert into city_lookup values('fresno', 'california');
insert into city_lookup values('monterey', 'california');

create table log_cities
(user_id int, visited_log varchar(512));

INSERT INTO log_cities values(123, 'This user was in dallas also probably in monterey');
INSERT INTO log_cities values(234, 'Logged: visisted tuscon');
INSERT INTO log_cities values(456, 'In March she visited texas, austin');
INSERT INTO log_cities values(567, 'He was probably here in phoenix and austin');

Query

select 
      user_id,
      case
        when visited_log like '%dallas%' then 'texas'
        when visited_log like '%austin%' then 'texas'
        when visited_log like '%phoenix%' then 'arizona'
        when visited_log like '%tuscon%' then 'arizona'
        when visited_log like '%fresno%' then 'california'
        when visited_log like '%monterey%' then 'california'
        else 'None' end visited_state
from
      log_cities;

Input & Output

-- Actual output
123     texas
234     arizona
456     texas
567     arizona

-- Actual output expected
123     texas
123     california
234     arizona
456     texas
567     arizona
567     texas

Answer 1

You need to JOIN the city_lookup table to the log_cities table to get all the cities visited by a user:

SELECT user_id,
       state
FROM city_lookup c
JOIN log_cities l ON l.visited_log LIKE CONCAT('%', c.city, '%')
ORDER BY user_id, state

Output:

user_id     state
123         california
123         texas
234         arizona
456         texas
567         arizona
567         texas

Demo on SQLFiddle

Answer 2

You can use a string_split to achieve this.

select user_id, state
from log_cities lc
outer apply STRING_SPLIT(lc.visited_log, ' ') s
join city_lookup cl on cl.city = s.value

Fiddle