2 Writing Basic SELECT Statements

1-2 Copyright  Oracle Corporation, All rights reserved. Capabilities of SQL SELECT Statements Selection Projection Table 1 Table 2 Table 1 Join

1-3 Copyright  Oracle Corporation, All rights reserved. Basic SELECT Statement SELECT[DISTINCT] {*, column [alias],...} FROMtable; SELECT[DISTINCT] {*, column [alias],...} FROMtable; SELECT identifies what columns. FROM identifies which table. SELECT identifies what columns. FROM identifies which table.

1-4 Copyright  Oracle Corporation, All rights reserved. Writing 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  Oracle Corporation, All rights reserved. Selecting All Columns DEPTNO DNAME LOC ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SQL> SELECT * 2 FROM dept;

1-6 Copyright  Oracle Corporation, All rights reserved. Selecting Specific Columns DEPTNO LOC NEW YORK 20 DALLAS 30 CHICAGO 40 BOSTON SQL> SELECT deptno, loc 2 FROM dept;

1-7 Copyright  Oracle Corporation, All rights reserved. Column Heading 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  Oracle Corporation, All rights reserved. Arithmetic Expressions Create expressions on NUMBER and DATE data by using arithmetic operators. Operator + - * / Description Add Subtract Multiply Divide

1-9 Copyright  Oracle Corporation, All rights reserved. Using Arithmetic Operators SQL> SELECT ename, sal, sal FROMemp; ENAME SAL SAL KING BLAKE CLARK JONES MARTIN ALLEN rows selected.

1-10 Copyright  Oracle Corporation, All rights reserved. Operator 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  Oracle Corporation, All rights reserved. Operator Precedence SQL> SELECT ename, sal, 12*sal FROM emp; ENAME SAL 12*SAL KING BLAKE CLARK JONES MARTIN ALLEN rows selected.

1-12 Copyright  Oracle Corporation, All rights reserved. Using Parentheses SQL> SELECT ename, sal, 12*(sal+100) 2 FROM emp; ENAME SAL 12*(SAL+100) KING BLAKE CLARK JONES MARTIN rows selected.

1-13 Copyright  Oracle Corporation, All rights reserved. Defining 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. ENAME JOB SAL COMM KING PRESIDENT 5000 BLAKE MANAGER TURNER SALESMAN rows selected. SQL> SELECT ename, job, sal, comm 2 FROM emp;

1-14 Copyright  Oracle Corporation, All rights reserved. Null Values in Arithmetic Expressions Arithmetic expressions containing a null value evaluate to null. SQL> select ename, 12*sal+comm 2 from emp 3 WHERE ename='KING'; ENAME 12*SAL+COMM KING

1-15 Copyright  Oracle Corporation, All rights reserved. Defining a Column Alias Renames a column heading Is useful with calculations Immediately follows column name; optional AS keyword between column name and alias Requires double quotation marks if it contains spaces or special characters or is case sensitive Renames a column heading Is useful with calculations Immediately follows column name; optional AS keyword between column name and alias Requires double quotation marks if it contains spaces or special characters or is case sensitive

1-16 Copyright  Oracle Corporation, All rights reserved. Using Column Aliases SQL> SELECT ename AS name, sal salary 2 FROM emp; NAME SALARY SQL> SELECT ename "Name", 2 sal*12 "Annual Salary" 3 FROM emp; Name Annual Salary

1-17 Copyright  Oracle Corporation, All rights reserved. Concatenation Operator Concatenates columns or character strings to other columns Is represented by two vertical bars (||) Creates a resultant column that is a character expression Concatenates columns or character strings to other columns Is represented by two vertical bars (||) Creates a resultant column that is a character expression

1-18 Copyright  Oracle Corporation, All rights reserved. Using the Concatenation Operator SQL> SELECTename||job AS "Employees" 2 FROM emp; Employees KINGPRESIDENT BLAKEMANAGER CLARKMANAGER JONESMANAGER MARTINSALESMAN ALLENSALESMAN rows selected.

1-19 Copyright  Oracle Corporation, All rights reserved. Literal Character Strings A literal is a character, a number, or a date included in the SELECT list. Date and character literal values must be enclosed within single quotation marks. Each character string is output once for each row returned. A literal is a character, a number, or a date included in the SELECT list. Date and character literal values must be enclosed within single quotation marks. Each character string is output once for each row returned.

1-20 Copyright  Oracle Corporation, All rights reserved. Using Literal Character Strings Employee Details KING is a PRESIDENT BLAKE is a MANAGER CLARK is a MANAGER JONES is a MANAGER MARTIN is a SALESMAN rows selected. Employee Details KING is a PRESIDENT BLAKE is a MANAGER CLARK is a MANAGER JONES is a MANAGER MARTIN is a SALESMAN rows selected. SQL> SELECT ename||' is a '||job 2 AS "Employee Details" 3 FROM emp;

1-21 Copyright  Oracle Corporation, All rights reserved. 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 rows selected.

1-22 Copyright  Oracle Corporation, All rights reserved. Eliminating Duplicate Rows Eliminate duplicate rows by using the DISTINCT keyword in the SELECT clause. SQL> SELECT DISTINCT deptno 2 FROM emp; DEPTNO