SUBSTR function in Sql

The SUBSTR functions allows you to extract a substring from a string. The syntax for the substr function is:

SUBSTR ( string, start_position, [ length ] )

Where

• string is the source string.
• start_position is the position for extraction. The first position in the string is always 1.
• length is optional. It is the number of characters to extract. If this parameter is omitted, substr will return the entire string.

Note:

• If start_position is 0, then SUBSTR treats start_position as 1 (ie: the first position in the string).
• If start_position is a positive number, then SUBSTR starts from the beginning of the string.
• If start_position is a negative number, then SUBSTR starts from the end of the string and counts backwards.
• If length is a negative number, then SUBSTR will return a NULL value.

For Example:

1. SUBSTR ('This is a Informatica blog', 11, 11) return 'Informatica'
2. SUBSTR ('This is a Informatica blog', 11) return 'Informatica blog'
3. SUBSTR ('This is a Informatica blog', -4, 4) return 'Blog'
4. SUBSTR ('This is a Informatica blog', -16, 4) return 'Info'