How to unescape % in LIKE clause - sql

Question

I have my search patterns stored in database in patterns table. For example my table column name_pattern contains string 'Basic%'. I'd like to create dynamic search where search patterns will be fetched from name_pattern column.
So my SQL query should look something like:
SELECT *
FROM products
WHERE product_name LIKE name_pattern <-- somehow joined from patterns table
Seems that Oracle escapes % in my string but I want to take it unescapped in order my query to work like:
SELECT *
FROM products
WHERE product_name LIKE 'Basic%'
I found that my problem is with stable set of rows:
CREATE TABLE patterns(code CHAR(1),name_pattern VARCHAR2(20));
INSERT INTO patterns(code,name_pattern) VALUES('B','Basic%');
INSERT INTO patterns(code,name_pattern) VALUES('T','%thing');
CREATE TABLE products (id NUMBER,name VARCHAR2(20),code CHAR(1));
INSERT INTO products(id,name,found) VALUES(1,'Basic instinct',NULL);
INSERT INTO products(id,name,found) VALUES(2,'Basic thing',NULL);
INSERT INTO products(id,name,found) VALUES(3,'Super thing',NULL);
INSERT INTO products(id,name,found) VALUES(4,'Hyper instinct',NULL);
MERGE INTO products p USING
(
SELECT code,name_pattern FROM patterns
) s
ON (p.name LIKE s.name_pattern)
WHEN MATCHED THEN UPDATE SET p.code=s.code;
SELECT * FROM products;
If my search patterns were Basic% and Super% in patterns table then this MERGE will work, but if my search patterns are Basic% and %thing, the second product should be marked with both codes 'B' and 'T' and that causes the error:
ORA-30926: unable to get a stable set of rows in the source tables
So my problem is not in (un)escaping :-(, sorry

Answer 1

You don't have to (un)escape anything, I'd say.
SQL> with
2 patterns (name_pattern) as
3 (select 'Basic%' from dual union all
4 select '%foot%' from dual
5 ),
6 products (id, name) as
7 (select 1, 'Basic instinct' from dual union all
8 select 2, 'Visual Basic' from dual union all
9 select 3, 'Littlefoot' from dual union all
10 select 4, 'Happy feet' from dual
11 )
12 select b.id, b.name, a.name_pattern
13 from products b join patterns a on b.name like a.name_pattern;
ID NAME NAME_P
---------- -------------- ------
1 Basic instinct Basic%
3 Littlefoot %foot%
SQL>
Based on test case you provided: don't merge, update!
SQL> update products p set
2 p.found = 1
3 where exists (select null
4 from patterns o
5 where p.name like o.name_pattern
6 );
3 rows updated.
SQL> select * from products;
ID NAME FOUND
---------- -------------------- ----------
1 Basic instinct 1
2 Basic thing 1
3 Super thing 1
4 Hyper instinct 0
SQL>
After you changed your mind (again), it is still update. Though, you didn't explain which code you want to take when there's multiple match (for example, product 2 matches both "Basic%" and "%thing") so I took any of them, using the min function.
SQL> update products p set
2 p.code = (select min(o.code)
3 from patterns o
4 where p.name like o.name_pattern
5 );
4 rows updated.
SQL> select * from products;
ID NAME CODE
---------- -------------------- ----------
1 Basic instinct B
2 Basic thing B
3 Super thing T
4 Hyper instinct NULL
SQL>