Index on Text Columns

When it can be used:

1. Exact matches:

• SELECT * FROM table WHERE x = 'sql'

2. Using wild card character (% or _) at the end:

• SELECT * FROM table WHERE x LIKE 'sq%'

3. Less effective, but still useful, using wild card character in the middle:

• SELECT * FROM table WHERE x LIKE 's_l'

When it is useless:

When wild card character is used in the beginning:

• SELECT * FROM table WHERE x LIKE '%ex'