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expressions. This type of function returns a single numeric value.
6. Metadata functions retrieve information about a specified database, such as its name and
database objects.
7. Security functions provide information that you can use to manage the security of a
database, such as information about database users and roles.
8. String functions perform operations on string values and return either numeric or string
values.

Using string functions, you can, for example, combine data, extract a substring, compare strings,
or convert a string to all uppercase or lowercase characters.

9. System functions perform operations and return information about values, objects, and
settings for the current SQL instance
10. System statistical functions provide various statistics about the current SQL instance – for
example, so that you can monitor the system's current performance levels.

Examples

Character modifications

Character modifying functions include converting characters to upper or lower case characters,
converting numbers to formatted numbers, performing character manipulation, etc.

The lower(char) function converts the given character parameter to be lower-cased characters.

SELECT customer_id, lower(customer_last_name) FROM customer;

would return the customer's last name changed from "SMITH" to "smith".

Date And Time

In SQL, you use date and time data types to store calendar information. These data types include
the time, date, smalldatetime, datetime, datetime2, and datetimeoffset. Each data type has a
specific format.

Data type Format

time hh:mm:ss[.nnnnnnn]

date YYYY-MM-DD

smalldatetime YYYY-MM-DD hh:mm:ss

datetime YYYY-MM-DD hh:mm:ss[.nnn]

datetime2 YYYY-MM-DD hh:mm:ss[.nnnnnnn]

datetimeoffset YYYY-MM-DD hh:mm:ss[.nnnnnnn] [+/-]hh:mm

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