oracle查询以使用IN运算符选择值

Question

I have a string which has list of valid places.

var locations = COLOMBO,DELHI,SINGAPORE

I want to query all the employees belonging to the location mention in the above string

I am using the following query

SELECT emp_id,emp_name 
FROM EMPLOYEE 
WHERE emp_location IN (locations) ;

Oracle is considering it as single string and searching for the below query string

SELECT emp_id,emp_name 
FROM EMPLOYEE 
WHERE emp_location IN ('COLOMBO,DELHI,SINGAPORE');

I want to know if there is any way I can pass the string and get the valid emp_id , emp_name belonging to the location mentioned in the string.

Answer 1

As mentioned here

First you need to use the REGEXP_SUBSTR function to split the string into individual strings

VAR locations = 'COLOMBO,DELHI,SINGAPORE';

SELECT REGEXP_SUBSTR(locations,'[^,]+', 1, level) 
FROM dual
CONNECT BY REGEXP_SUBSTR(locations, '[^,]+', 1, level) IS NOT NULL;

Then use it as a sub query in a select to get the desired result

VAR locations = 'COLOMBO,DELHI,SINGAPORE';

SELECT emp_id,emp_name FROM EMPLOYEE 
WHERE emp_location in(
SELECT REGEXP_SUBSTR(locations,'[^,]+', 1, level) FROM dual
CONNECT BY REGEXP_SUBSTR(locations, '[^,]+', 1, level) IS NOT NULL);

Answer 2

You are looking for locations mentioned in the string, so actually for locations that are a substring of your string. Oracle offers INSTR for such a search.

Only be aware to look for complete cities from comma to comma (add commas in front and end). So not to find 'YORK' in 'LONDON,NEW YORK' (for ',YORK,' is not a substring of ',LONDON,NEW YORK,' wheras 'YORK' without commas would be a substring of 'LONDON,NEW YORK').

select emp_id,emp_name 
from EMPLOYEE 
where instr(','|| locations || ',' , ',' || emp_location || ',') > 0;