HP Neoview SQL Reference Manual page 179

600 1500
600 1500
900 2500
900 1000
. . .
In this example, because of READ UNCOMMITTED access, the query does not wait for
other concurrent processes to commit rows.
• Display selected rows grouped by job code in ascending order:
SELECT jobcode, AVG(salary)
FROM persnl.employee
WHERE jobcode > 500 AND deptnum <= 3000
GROUP BY jobcode
ORDER BY jobcode;
JOBCODE EXPR
------- ----------------------
600
900
--- 2 row(s) selected.
This select list contains only grouping columns and aggregate functions. Each row of the
output summarizes the selected data within one group.
• Select data from more than one table by specifying the table names in the FROM clause and
specifying the condition for selecting rows of the result in the WHERE clause:
SELECT jobdesc, first_name, last_name, salary
FROM persnl.employee E, persnl.job J
WHERE E.jobcode = J.jobcode AND
E.jobcode IN (900, 300, 420);
JOBDESC
------------
SALESREP
SALESREP
...
ENGINEER
ENGINEER
...
SECRETARY
SECRETARY
...
--- 27 row(s) selected.
This type of condition is sometimes referred to as a join predicate. The query first joins the
EMPLOYEE and JOB tables by combining each row of the EMPLOYEE table with each row
of the JOB table; the intermediate result is the Cartesian product of the two tables.
This join predicate specifies that any row (in the intermediate result) with equal job codes
is included in the result table. The WHERE condition further specifies that the job code must
be 900, 300, or 420. All other rows are eliminated.
The four logical steps that determine the intermediate and final results of the previous query
are:
1. Join the tables.
EMPLOYEE Table
EMPNUM ...
JONATHAN
JIMMY
MIRIAM
SUE
29000.00
25100.00
FIRST_NAME LAST_NAME
------------ ---------------
TIM WALKER
HERBERT KARAJAN
MARK FOLEY
MARIA JOSEF
BILL WINN
DINAH CLARK
JOBCODE ...
MITCHELL
SCHNEIDER
KING
CRAMER
SALARY
-----------
32000.00
29000.00
33000.00
18000.10
32000.00
37000.00
JOB Table
SALARY JOBCODE
32000.00
26000.00
18000.00
19000.00
JOBDESC
SELECT Statement 179