Copyright Ó Oracle Corporation, 1998. All rights reserved.

1

Writing Basic SQL StatementsWriting Basic

SQL Statements

1-2 Copyright Ó Oracle Corporation, 1998. All rights reserved.

ObjectivesObjectives

At the end of this lesson, you should be able to:• List the capabilities of SQL SELECT

statements• Execute a basic SELECT statement• Differentiate between SQL statements

and SQL*Plus commands

At the end of this lesson, you should be able to:• List the capabilities of SQL SELECT

statements• Execute a basic SELECT statement• Differentiate between SQL statements

and SQL*Plus commands

1-3 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Basic SELECT StatementBasic SELECT Statement

SELECT [DISTINCT] {*, column [alias],...}FROM table;

SELECT [DISTINCT] {*, column [alias],...}FROM table;

• SELECT identifies what columns• FROM identifies which table

• SELECT identifies what columns• FROM identifies which table

1-4 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Writing SQL StatementsWriting SQL Statements

• SQL statements are not case sensitive. • SQL statements can be on one or

more lines.• Keywords cannot be abbreviated or split

across lines.• Clauses are usually placed on

separate lines.• Tabs and indents are used to enhance

readability.

• SQL statements are not case sensitive. • SQL statements can be on one or

more lines.• Keywords cannot be abbreviated or split

across lines.• Clauses are usually placed on

separate lines.• Tabs and indents are used to enhance

readability.

1-5 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Selecting All ColumnsSelecting All Columns

DEPTNO DNAME LOC--------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON

SQL> SELECT * 2 FROM dept;

1-6 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Selecting Specific ColumnsSelecting Specific Columns

DEPTNO LOC--------- ------------- 10 NEW YORK 20 DALLAS 30 CHICAGO 40 BOSTON

SQL> SELECT deptno, loc 2 FROM dept;

1-7 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Column Label DefaultsColumn Label Defaults

• Default justification– Left: Date and character data– Right: Numeric data

• Default display: Uppercase

• Default justification– Left: Date and character data– Right: Numeric data

• Default display: Uppercase

1-8 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Arithmetic ExpressionsArithmetic Expressions

Create expressions on NUMBER and DATE data types by using arithmetic operators.Create expressions on NUMBER and DATE data types by using arithmetic operators.

Operator

+

-

*

/

Description

Add

Subtract

Multiply

Divide

1-9 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Using Arithmetic OperatorsUsing Arithmetic Operators

SQL> SELECT ename, sal, sal+300 2 FROM emp;

ENAME SAL SAL+300---------- --------- ---------KING 5000 5300BLAKE 2850 3150CLARK 2450 2750JONES 2975 3275MARTIN 1250 1550ALLEN 1600 1900...14 rows selected.

1-10 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Operator PrecedenceOperator Precedence

• Multiplication and division take priority over addition and subtraction.

• Operators of the same priority are evaluated from left to right.

• Parentheses are used to force prioritized evaluation and to clarify statements.

• Multiplication and division take priority over addition and subtraction.

• Operators of the same priority are evaluated from left to right.

• Parentheses are used to force prioritized evaluation and to clarify statements.

** // ++ __

1-11 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Operator PrecedenceOperator Precedence

SQL> SELECT ename, sal, 12*sal+100 2 FROM emp;

ENAME SAL 12*SAL+100---------- --------- ----------KING 5000 60100BLAKE 2850 34300CLARK 2450 29500JONES 2975 35800MARTIN 1250 15100ALLEN 1600 19300...14 rows selected.

1-12 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Using ParenthesesUsing Parentheses

SQL> SELECT ename, sal, 12*(sal+100) 2 FROM emp;

ENAME SAL 12*(SAL+100)---------- --------- -----------KING 5000 61200BLAKE 2850 35400CLARK 2450 30600JONES 2975 36900MARTIN 1250 16200...14 rows selected.

1-13 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Defining a Null ValueDefining a Null Value• A null is a value that is unavailable,

unassigned, unknown, or inapplicable.• A null is not the same as zero or a blank

space.

• A null is a value that is unavailable, unassigned, unknown, or inapplicable.

• A null is not the same as zero or a blank space.

SQL> SELECT ename, job, comm 2 FROM emp;

ENAME JOB COMM---------- --------- ---------KING PRESIDENTBLAKE MANAGER...TURNER SALESMAN 0...14 rows selected.

1-14 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Null Values in Arithmetic Expressions

Null Values in Arithmetic Expressions

Arithmetic expressions containing a null value evaluate to null.Arithmetic expressions containing a null value evaluate to null.

SQL> select ename NAME, 12*sal+comm 2 from emp 3 WHERE ename='KING';

NAME 12*SAL+COMM ---------- -----------KING

1-15 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Duplicate RowsDuplicate Rows

The default display of queries is all rows, including duplicate rows.The default display of queries is all rows, including duplicate rows.

SQL> SELECT deptno 2 FROM emp;

SQL> SELECT deptno 2 FROM emp;

DEPTNO--------- 10 30 10 20...14 rows selected.

1-16 Copyright Ó Oracle Corporation, 1998. All rights reserved.

Eliminating Duplicate RowsEliminating Duplicate Rows

Eliminate duplicate rows by using the DISTINCT keyword in the SELECT clause.

SQL> SELECT DISTINCT deptno 2 FROM emp;

DEPTNO--------- 10 20 30