2 sql - single-row functions

Chapter 3
Selected Single-Row
Functions
and Advanced DML & DDL

Chapter Objectives
• Use the UPPER, LOWER, and INITCAP
functions to change the case of field
values and character strings
• Extract a substring using the SUBSTR
function
• Determine the length of a character string
using the LENGTH function

Chapter Objectives
• Use the LPAD and RPAD functions to pad a
string to a desired width
• Use the LTRIM and RTRIM functions to remove
specific characters strings
• Round and truncate numeric data using the
ROUND and TRUNC functions
• Calculate the number of months between two
dates using the MONTHS_BETWEEN function

Chapter Objectives
• Identify and correct problems associated with
calculations involving null values using the NVL
function
• Display dates and numbers in a specific format
with the TO_CHAR function
• Determine the current date setting using the
SYSDATE keyword
• Nest functions inside other functions
• Identify when to use the DUAL table

Terminology
• Function – predefined block of code that
accepts arguments
• Single-row Function – returns one row of
results for each record processed
• Multiple-row Function – returns one result
per group of data processed

Case Conversion Functions
Alter the case of data stored in a column
or character string

LOWER Function
Used to convert characters to lower-case
letters

UPPER Function
Used to convert characters to upper-case
letters

INITCAP Function
Used to convert characters to mixed-case

Character Manipulation
Functions
Manipulates data by extracting substrings,
counting number of characters, replacing
strings, etc.

SUBSTR Function
Used to return a substring, or portion of a string

LENGTH Function
Used to determine the number of characters in a
string

LPAD and RPAD Functions
Used to pad, or fill in, a character string to a
fixed width

LTRIM and RTRIM Functions
Used to remove a specific string of characters

REPLACE Function
Substitutes a string with another specified string

CONCAT Function
Used to concatenate two character strings

Number Functions
Allows for manipulation of numeric data

ROUND Function
Used to round numeric columns to a stated
precision

TRUNC Function
Used to truncate a numeric value to a specific position

Date Functions
Used to perform date calculations or
format date values

MONTHS_BETWEEN Function
Determines the number of months
between two dates

ADD_MONTHS Function
Adds a specified number of months to a date

NEXT_DAY Function
Determines the next occurrence of a
specified day of the week after a given
date

TO_DATE Function
Converts various date formats to the
internal format (DD-MON-YYYY) used by
Oracle9i

NVL Function
Substitutes a value for a NULL value

NVL2 Function
Allows different actions based on whether a
value is NULL

TO_CHAR Function
Converts dates and numbers to a
formatted character string

Format Model Elements –
Time and Number

Other Functions
• NVL
• NVL2
• TO_CHAR
• DECODE
• SOUNDEX

DECODE Function
Determines action based upon values in a list

SOUNDEX Function
References phonetic representation of
words

Nesting Functions
• One function is used as an argument inside
another function
• Must include all arguments for each function
• Inner function is resolved first, then outer
function

Summary of functions
Single-Row Functions
• Text Functions
lpad, rpad, lower, upper, initcap, length, substr, instr, trim,
concat
• Arithmetic Functions
abs, round, ceil, floor, mod, sign, sqrt, trunc, vsize
• List Functions
greatest, least, decode
• Date Functions
add_months, last_day, months_between, new_time,
next_day, round, trunc
• Conversion Functions
to_char, to_number, to_date

DUAL Table
• Dummy table
• Consists of one column and one row
• Can be used for table reference in the FROM
clause
Ex: select sysdate from dual

Advanced Data Selection in Oracle
Using a Subquery
Multiple-Row Subqueries
SELECT ename, job, sal
FROM emp
WHERE sal = (SELECT MIN(sal)
FROM emp);
SELECT empno, ename, job, sal
FROM emp
WHERE sal < ANY (SELECT sa FROM emp
WHERE job
AND job <> 'SALESMAN';
multiple-row comparison operators – IN, ANY,ALL

Manipulating Oracle Data
Inserting Rows with Null Values and Special Values
Copying Rows from Another Table
INSERT INTO emp (empno, ename, hiredate, jo
sal,comm, mgr, deptno)
VALUES (113,'Louis', SYSDATE, 'MANAGER', 69
NULL, NULL, 30);
INSERT INTO sales_reps(id, name, salary, co
SELECT empno, ename, sal, comm
FROM emp
WHERE job LIKE '%SALES%';

Creating and Managing
Database Objects (Tables)
Creating a Table by Using a Subquery
CREATE TABLE dept30
AS
SELECT empno, ename, sal*12 ANNSAL,
hiredate
FROM emp
WHERE deptno = 30;

Common Datatypes
Datatype Description
VARCHAR2(siz
e)
Variable-length character data, can up to
4,000 bytes.
CHAR(size) Fixed-length character data, can up to
2,000 bytes.
NUMBER(p.s) Variable-length numeric data, can up to 38
digits. E.g. Number(5.2)  999.99
DATE Date and time values, 7 bytes.
Other data types included: LONG, CLOB, RAW,
LONG RAW, BLOB, BFILE, ROWID … etc.

The Drop Table Statement
DROP TABLE table;
Dropping a Table
DROP TABLE dept30;

Other Database Objects (Views,
Sequences)Views
CREATE [OR REPLACE] [FORCE|NOFORCE] VIEW view
[(alias[, alias]...)]
AS subquery
[WITH CHECK OPTION [CONSTRAINT constraint]]
[WITH READ ONLY [CONSTRAINT constraint]];
DROP VIEW view;
To restrict data access
To make complex queries easy
To provide data independence
To present different views of the same data
You can retrieve data from a view as from a table.

Sequences)
Modifying a View
CREATE OR REPLACE VIEW empv30
(id_no, name, salary)
AS SELECT empno, ename, sal
FROM emp
WHERE deptno = 30;
Drop a View
DROP VIEW empv30
Creating a View
CREATE VIEW empv30
AS SELECT empno, ename, sal
FROM emp
WHERE deptno = 30;

Sequences)
Sequences
CREATE SEQUENCE sequence
[INCREMENT BY n]
[START WITH n]
[{MAXVALUE n | NOMAXVALUE}]
[{MINVALUE n | NOMINVALUE}]
[{CYCLE | NOCYCLE}]
[{CACHE n | NOCACHE}];
Automatically generates unique numbers
Is typically used to create a primary key
Replaces application code

Sequences)
Creating a Sequence
NEXTVAL and CURRVAL Pseudocolumns
CREATE SEQUENCE deptid_seq
INCREMENT BY 10
START WITH 5
MAXVALUE 9999;
NEXTVAL returns the next available sequence
value. It returns a unique value every time it is
referenced, even for different users
CURRVAL obtains the current sequence value.
NEXTVAL must be issued for that sequence before
CURRVAL contains a value

Sequences)
Using a Sequence
View the current value
Removing a Sequence
INSERT INTO dept(deptno, dname, loc)
VALUES (deptid_seq.NEXTVAL,'Support',
' HONG KONG' );
SELECT deptid_seq.CURRVAL
FROM dual;
DROP SEQUENCE deptid_seq;

Appendix B: Useful link
• Try these with SQL
http://www.cse.cuhk.edu.hk/~csc3170/tutorial/index.
html
• http://db00.cse.cuhk.edu.hk
• http://www.db.cs.ucdavis.edu/teaching/sqltutorial
• http://www.w3schools.com/sql

2 sql - single-row functions

More Related Content

What's hot (20)

Similar to 2 sql - single-row functions (20)

More from Ankit Dubey (20)

Recently uploaded (20)

2 sql - single-row functions