The NOW() function is an aggregate function used to return the date and time along with other column.

The NOW() function returns the result as dd/mm/yyyy HH:MM:SS AM/PM depending on your regional settings.

SQL NOW() Syntax

The LEN function is useful to count the number of characters in a column you specified as the parameter. LEN is short for length. The LEN function returns the number of characters including spaces or any character within that column.

You can use SQL Alias to name the result of the LEN function.

SQL LEN() Syntax

The FORMAT() function is normally applied on formatting column with Date value like YYYY, MM, and DD.

SQL FORMAT() Syntax

The UNIQUE Contraints identifies a record in a database table uniquely. Unlike PRIMARY KEY contraints, you can have many UNIQUE contraint in a table.

UNIQUE Contraints Syntax - MySQL

The UNION Operator is used to combine the result set of two or more SELECT Statement. This operator is useful if you have two table that share the same column name and data type and you want to combine it in a single Query.

Take note that both table must have the same column name and data type.

The DEFAULT Constraint is used to insert the default values into a column during design time.

The default values is used in new record if no value is specified during INSERT Statement.

The default

SQL DEFAULT Constraint Syntax

COUNT is a simple aggregate function provided by SQL. As it is clear from its name that it simply counts the number of records in the table and returns the total count.

There are three (3) different usage for the Count function.

• SQL COUNT(column_name)
• COUNT(*)
• COUNT(DISTINCT column_name)

Consider the following table for this exercise

Employess