Advanced SQL Topics: MAKE_SET Function

The MAKE_SET function is useful to build up a set of bit values to represent a set of set members. This function takes a list of strings as input and returns a string containing a comma-separated list of set members.

Syntax

The syntax for the MAKE_SET function is as follows:

MAKE_SET(bits, str1[, str2, ..., strN])

Here:

• bits - An integer value that specifies the number of bits to represent each set member.
• str1[, str2, ..., strN] - One or more string values to be included in the set.

Example

Consider the following example:

SELECT MAKE_SET(2, 'apple', 'orange', 'banana', 'grape');

Output

The output for the above example will be:

0101

Explanation

In the above example, the output is a string representation of a set containing four members. The bits parameter is set to 2, which means that each member is represented using a 2-bit value. The set contains four members: 'apple', 'orange', 'banana' and 'grape'. The output string contains a comma-separated list of 2-bit values for each member, in the same order as they were specified in the input.

• 'apple' = 01
• 'orange' = 10
• 'banana' = 11
• 'grape' = 00

The resulting bit string is 0101, which represents the set {apple, orange, banana, grape}.

Use

The MAKE_SET function can be used in a variety of applications, such as:

• Creating bit-mapped representations of sets for storage or transport.
• Comparing sets based on their bit-mapped representations.
• Building dynamic queries based on set membership.

Important Points

• The maximum number of members that can be represented in a set is 64.
• The MAKE_SET function is not case-sensitive, so 'apple' and 'APPLE' are treated as the same member.
• If two or more members have the same name, only the first one will be included in the set.
• If a member name contains a comma or a backslash character, it will be escaped with a backslash in the output.

Summary

The MAKE_SET function is a powerful tool in SQL that allows you to build up sets of bit values to represent a set of set members. This function is useful for a variety of applications, such as storing or transmitting sets, comparing sets based on their bit-mapped representations, and building dynamic queries based on set membership. You can use the MAKE_SET function to create bit-mapped representations of sets and compare them based on their bit values. Just remember to keep in mind the important points mentioned above when working with this function.