String over columns

Normally a string can be searched for across many columns using the OR function but this is not efficient as this could lead to errors while using a CONCAT function ( || for oracle, + for sqlserver) could do the same task but can get rid of the risk of errors

schema:scott

DROP TABLE bedrooms 

 CREATE TABLE bedrooms(  name VARCHAR(20),  floorcolor VARCHAR(20),  ceilingcolor VARCHAR(20),  wallcolor VARCHAR(20)); INSERT INTO bedrooms VALUES ('Jim','RED','GREEN','YELLOW'); INSERT INTO bedrooms VALUES ('Bob','YELLOW','BLUE','BLACK'); INSERT INTO bedrooms VALUES ('Allan','BLUE','PINK','BLACK'); INSERT INTO bedrooms VALUES ('George','BLUE','GREEN','OAK'); 

SELECT name FROM bedrooms WHERE floorcolor = 'YELLOW' OR ceilingcolor = 'YELLOW' OR wallcolor = 'YELLOW' 

Using OR increases the chances for careless mistakes instead CONCAT could be used to make the query more efficient.

To avoid problems make sure to add in separators and if a value can be null make sure to use it is wrapped in COALESCE or NVL for example:

COALESCE(floorcolor,' ').

SELECT name FROM bedrooms  WHERE ':' || floorcolor || ':' || ceilingcolor || ':' || wallcolor || ':'  LIKE '%:YELLOW:%' 

SELECT name FROM bedrooms  WHERE ':' + floorcolor + ':' + ceilingcolor + ':' + wallcolor + ':'  LIKE '%:YELLOW:%' 

SELECT name FROM bedrooms  WHERE CONCAT (':',floorcolor,':',ceilingcolor,':',wallcolor,':')  LIKE '%:YELLOW:%' 

Instead of COALESCE or NVL, IFNULL can be used.

Instead of COALESCE or NVL, IFNULL can be used.

SQL HACKS

Hack 10 Converting subqueries into joins

Hack 11 Converting aggregate subqueries into joins

Hack 14 Generate Combinations

Hack 16 Search for a String across columns

Hack 24 Multiply Across a Result Set

Hack 25 Keep a running total

Hack 25.5 Splitting and combining columns

Hack 26 Include the rows your JOIN forgot

Hack 30 Calculate the maximum/minimum of two fields

Hack 33 Get values and subtotals in one shot

Hack 50 Combine tables containing different data

Hack 51/52 Display rows as columns

Hack 55 Import Someone Else's Data

Hack 62 Issue Queries Without Using a Table

Hack 63 Generate rows without tables

Hack 70 Combine your queries

Hack 72 Extract a subset of the results

Hack 78 Break it down by Range

Hack 88 Test two values from a subquery

Hack 98 Find and stop long running queries

Hack 100 Run SQL from a Web Page