SQL Query Extras MIS 433

Rerunning the last Query n Type the forward slash “/” to rerun the last query that was entered

Aliases for Field Names n You can replace the name of the field name with an Alias. For example: SQL> Select first as FirstName, last as LastName, total_commission as “Total Commission” from sales_rep FIRSTNAM LASTNAME Total Commission Mary Jones 2150 William Smith Miguel Diaz 2150 Note : Spaces are not allowed unless a double quote is used. In addition, the width of the column is defined by the field width not the alias

Ordering Calculated Columns n If you want to use a calculated column to sort your output, you can use the column number to specify a column to order the output SQL> select city, state, balance*1.05 from customer order by 3 CITY ST BALANCE* Grant MI Ada MI

Prompting for user Input n Use the PROMPT command to request input from a user. n Use the Accept command to accept input PROMPT Enter a title up to 30 characters long. ACCEPT MYTITLE PROMPT 'Title: ' TTITLE LEFT MYTITLE SKIP 2 SELECT * FROM CUSTOMER WHERE BALANCE>1000

Prompting for Input n Run the command file: SQL> START PROMPT1 Enter a title up to 30 characters long. Title: Department Report as of 1/1/95 n SQL*Plus displays the following output: Department Report as of 1/1/95 DEPTNO DNAME LOC ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON

Prompts for Variable Input n You can also pass information to a query: SQL> SELECT last, city, state FROM CUSTOMER where city = ‘&city’

Prompts for Variable Input n The prompt will ask for the City Name SQL> select last, city, state from customer where city = '&city' Enter value for city: Grant old 2: where city = '&city' new 2: where city = 'Grant' LAST CITY ST Samuels Grant MI Williams Grant MI Martin Grant MI

Storing Query Statements n SQL statements may be saved and used over again. The commands used are SAVE, GET, and START –Run a query, then type SAVE FILENAME No extension is needed (it will be *.sql) SQL> get cust-bal 1 Select * from customer 2* where balance>500 SQL> save cust-bal Created file cust-bal

Retrieving Query Statements n Saved SQL statements may be retrieved. The commands used are GET or START –Get: retrieves the saved statement and displays it on the screen. SQL> get cust-bal 1 Select * from customer 2* where balance>500; –Start: runs the saved statement. SQL> start cust-bal

Storing and Printing Query Results n Options –Send query results to a file to edit with a word processor –To store the results of a query in a file, enter the SPOOL command: SPOOL file_name –SQL*Plus continues to spool information to the file until spooling is turned off: SPOOL OFF

Pausing Output n You can pause output at the end of each screen full of information. SQL> set pause on n You can turn the pause off. SQL> set pause off

Changing Line Lengths n Normally your output will be set to 80 characters. You can change the line length to a longer setting using the following command: SQL> set linesize 132 –This command will change the line size to 132 characters. n A similar command changes the length of the page(the default is 22 or 24 lines) SQL> set pagesize 66

Changing Field Lengths in Output n Sometimes you will find that the fields for character strings are much longer than are needed in your output. You can use the substring function to shorted a field’s length. SQL> select substr(city,1,7) as City from customer CITY Lansing Grant etc.

Spooling to the Printer n To print query results, spool the results to a file. n Instead of typing SPOOL OFF, enter the command to output to the system printer: SPOOL OUT n SQL*Plus stops spooling to the file and copies the contents of the spooled file to default printer.

Altering tables: Do’s and Don’ts n Restricted Actions –Changing a column’s data type, size, and default values is allowed only if there are no data in the columns being modified. –Adding a primary key is allowed only if current field values are unique. –Adding UNIQUE and CHECK CONDITION constraints to a column is allowed only if current field values match the added condition. –Adding a foreign key is allowed only if current field values are NULL or exist in the referenced table. –Changing a column name is NOT allowed. –Deleting a column (e.g., ALTER TABLE table_name DROP COLUMN column_name;

Altering tables: Do’s and Don’ts n Unrestricted Actions –Adding a new column to a table. –Deleting a primary key constraint (also removes any foreign key references to the field in other tables). –Deleting a foreign key constraint.

Options for Altering a Table ALTER TABLE Table_nameADD column-definition MODIFY column-nameDEFAULT value DROP DEFAULT ADDprimary-key-definition foreign-key-definition null check-constraint DROP CONSTRAINT column-nameCASCADE RESTRICT

Examples of Altering Tables ALTER TABLE Part MODIFY (warehouse_number INTEGER) ALTER TABLE Part ADD CONSTRAINT item_class check in (‘HW’, ‘AP’, ‘SG’) ALTER TABLE Part MODIFY (item_class DEFAULT ‘HW’;) ALTER TABLE Part DROP CONSTRAINT item_class

Options for Alter Table n Use ALTER TABLE / ADD to… –Add a new column –Add a new foreign key or check condition constraint n Use ALTER TABLE / MODIFY to… –Modify a column’s data type or size –modify a column to add a NOT NULL constraint –Modify a column to add a default value

Creating an Auto-Number Sequence n Sequences are sequential lists of numbers that are generated automatically by SQL. –Used to create a unique key value for a table when no “natural” key value exists. –Used for numeric fields only

Sequence Syntax CREATE SEQUENCE [INCREMENT by ] [START WITH ] [MAXVALUE ] [MINVALUE ] {for decreasing sequences} [ORDER] {ensures proper ordering} [CACHE]{sequence numbers are cached to improve performance}

An Example of Sequence SQL> CREATE SEQUENCE customer_sequence start with 623 nomaxvalue nocache; SQL> INSERT INTO customer VALUES (customer_sequence.nextval,’Bolean',’Robert', ’4431 Sycamore', 'Lansing', 'MI', '49224', , 1322,'03');

Renaming a table n You can change the name of a table RENAME oldtablename TO newtablename

You can Reformat Columns n Changing a Column Heading –To produce a report from sales_rep with new headings specified for various columns, enter the following commands: clear columns COLUMN slsrep_number HEADING 'Sales Rep #' format a12 COLUMN Last HEADING 'Last Name' format a12 COLUMN First HEADING 'First Name' format a12 COLUMN Street HEADING 'Street Address' format a15 Select slsrep_number, first, last, street, total_commission as Commission from sales_rep

Reformatting Columns n SQL*Plus displays the following output: Sales Rep # First Name Last Name Street Address COMMISSION Mary Jones 123 Main William Smith 102 Raymond Miguel Diaz 419 Harper 2150 – Note : The new headings will remain in effect until you enter different headings, reset each column's format, or exit from SQL*Plus.

Word Wrap for Text Output n WRAP or WORD_WRAP can be used at the end of a Column Format statement to shorten the column length but not lose information. SQL> column street heading 'ST' format a6 word_wrap SQL> select city, street from customer 2 where city='Grant'; CITY ST Grant 215 Pete Grant 519 Watson Grant 419 Chip