Character Functions in SQL

• Case-manipulation functions
• LOWER   :- Converts alpha character values to lowercase.
• UPPER   :-  Converts alpha character values to uppercase.
• INITCAP  :-  Converts alpha character values to uppercase for the first letter of               each word.
• Character-manipulation functions
• CONCAT  :-  Concatenates the first character values to second character value.
• SUBSTR  :-  Return specified characters from character value.
• LENGTH  :-  Returns the number of character in the expression.
• INSTR  :-  Returns the numeric position of a named string.
• LPAD  :-  Pads the character value right justified to a total width of n.
• RPAD  :- Pads the character value left justified to a total width of n.
• TRIM  :-  Enables you to trim heading or trailing characters from a character string.
• REPLACE  :-  Searches a text expression for a character string and if found, replaces it with a specified replacement string.

Example:

LOWER

UPPER & INITCAP

CONCAT

SUBSTR

LENGTH

INSTR

LPAD & RPAD

TRIM

Unit 3 :- Single-Row Functions

Functions are very powerful feature of SQL and can be used to do the following:

• Perform calculations on data.
• Modify individual data items.
• Manipulate output for groups of rows.
• Format dates and numbers for display.
• Convert column data types.

SQL functions sometimes take arguments and always return a value.

There are Two distinct types of functions:

• Single-row functions.
• Multiple-row functions.

Single-Row Functions

These functions operate on single rows only and return one result per row. There are different types single-row functions. This section covers the following ones:

• Character
• Case-manipulation functions
• LOWER
• UPPER
• INITCAP
• Character-manipulation functions
• CONCAT
• SUBSTR
• LENGTH
• INSTR
• LPAD   |   RPAD
• TRIM
• REPLACE
• Number
• ROUND
• TRUNC
• MOD
• Date
• MONTHS_BETWEEN
• ADD_MONTHS
• NEXT_DAY
• LAST_DAY
• ROUND
• TRUNC
• Conversion
• Implicit data type conversion
• VARCHAR2 OR CHAR -----   TO -----   NUMBER
• VARCHAR2 OR CHAR -----   TO -----   DATE
• NUMBER                       -----    TO -----  VARCHAR2
• DATE                              -----    TO ----    VARCHAR2
• Explicit data type conversion
• TO_CHAR
• TO_DATE
• TO_NUMBER
• General
• NVL
• NVL2
• NULLIF
• COALESCE
• CASE
• DECODE

Multiple-Row Functions

Functions can manipulate groups of rows to give one result per group of rows. These functions are known as group functions. This is covered in next Unit.

SORTING in SQL

The default sort order is ascending:

• Numeric values are displayed with the lowest value first e.g. 1-10
• Date values are displayed with the earliest value first e.g. 01-JAN-12 before 12-FEB-13
• Character values are displayed in alphabetical order e.g. A first Z last
• Null values are displayed last for ascending sequence and first for descending sequence.

Sorting in DESCENDING Order

Sorting by Column Alias

We can use a column alias in the ORDER BY clause. The below example sorts the data by Annual Salary.

Example:

Sorting By Multiple Columns:

We can sort query by more than one column. The sort limit is the number of columns in the given table.

Example:

ORDER BY Clause in SQL

• Sort rows with the ORDER BY clause
• ASC:  ascending order (Default)
• DESC:  descending order
• The ORDER BY clause comes last in the SELECT statement.
• We can Sort the rows by the name of the column which may not be present in the sorted list. (see second example)

Example:

Example: Here names of employees are sorted according to salary but salary column is not present in the sorting list.