Using SQL Queries to Insert, Update, Delete, and View Data

1. Using SQL Queries to Insert,Update, Delete, and View Data Chapter 3 Guide to Oracle10G

2. Lesson A Objectives • Learn how to run a script to create database tables automatically • Learn how to insert data into database tables • Learn how to create database transactions and commit data to the database • Create search conditions in SQL queries • Understand how to update and delete database records, and how to truncate tables • Learn how to create and use sequences to generate surrogate key values automatically • Learn how to grant and revoke database object privileges Guide to Oracle10G

3. Using Scripts to Create Database Tables • One or more SQL commands saved in a text file • Usually have .sql extension • To run from SQL*Plus: • Start full file path (c:\temp\myfile.sql) • Ex: start c:\temp\myfile.sql • @full file path (@c:\temp\myfile.sql) • Ex: @c:\temp\myfile.sql • Extension can be omitted if it is .sql Guide to Oracle10G

4. Inserting Data into Tables • INSERT command adds new records • Field values should match column order, or be specified in command • INSERT INTO faculty (F_ID, F_LAST, F_FIRST, F_MI, LOC_ID) VALUES (1, 'Cox', 'Kim', 'J', 9); Guide to Oracle10G

5. Format Models • Used to format data retrieved from database • Can be used to format a date to display time or a number to display as a currency Guide to Oracle10G

6. Numerical Format Models Guide to Oracle10G

7. Date Format Models Guide to Oracle10G

8. Date Format Models Guide to Oracle10G

9. Inserting Date and Interval Values • Use to_date function to convert a character string to a date • Specify date string and matching format model • TO_DATE('08/24/2004', 'MM/DD/YYYY') • TO_DATE('10:00 AM', 'HH:MI AM') Guide to Oracle10G

10. Creating Transactions and Committing New Data • Transaction: series of action queries that represent a logical unit of work • User can commit (save) changes • User can roll back (discard) changes • Pending transaction: a transaction waiting to be committed or rolled back • Oracle DBMS locks records associated with pending transactions • Other users cannot view or modify locked records Guide to Oracle10G

11. Commit and Roll Back in SQL*Plus • Transactions begin automatically with first command • Type COMMIT to commit changes • Type ROLLBACK to roll back changes Guide to Oracle10G

12. Creating Search Conditions in SQL Queries • An expression that seeks to match specific table records • Used in SELECT, UPDATE and DELETE statements • WHERE fieldnamecomparison_operatorsearch_expression • WHERE S_ID = 1 Guide to Oracle10G

13. Comparison Operators Guide to Oracle10G

14. Defining Search Expressions • Character strings • Must be enclosed in single quotes • Case sensitive • Dates • Use to_date function with date string and format model Guide to Oracle10G

15. Creating Complex Search Conditions • Combines multiple search conditions using the AND,OR, and NOT logical operators. • AND – both conditions must be true • OR – one or both condition must be true • NOT – opposite of actual value • Use () to group logical operators Guide to Oracle10G

16. Updating and Deleting Existing Table Records • UPDATE: • Updates field values in one or more records in a table • Only one table may be updated at a time • UPDATE tablename SET field1= new_value1, field2 = new_value2, ... WHERE search condition; • DELETE: • Removes specific records from a database table • If search condition is omitted, entire table data is removed • DELETE FROM tablename WHERE search condition; Guide to Oracle10G

17. Updating and Deleting Existing Table Records • TRUNCATE • Removes all of the table data without saving any rollback information • Must disable foreign key constraints before truncating table • TRUNCATE TABLE tablename; Guide to Oracle10G

18. Sequences • Sequential lists of numbers to create unique surrogate key values • To use a sequence: • SELECT sequence_name.NEXTVAL FROM DUAL; • INSERT INTO location LOC_ID) VALUES(loc_id_sequence.NEXTVAL); Guide to Oracle10G

19. Database Object Privileges • Privileges must be granted so that other users can access objects in user schema • GRANT privilege1, privilege2,…ON object_name TO user1,user2,...; • REVOKE privilege1, privilege2,... ON object_name FROM user1, user2, ...; • To grant or revoke privileges for everyone use PUBLIC as user Guide to Oracle10G

20. Lesson B Objectives • Learn how to write SQL queries to retrieve data from a single database table • Create SQL queries that perform calculations on retrieved data • Use SQL group functions to summarize retrieved data Guide to Oracle10G

21. Retrieving Data from a Single Database Table • SELECT fieldname1, fieldname2, ... FROM ownername.tablename WHERE search_condition; • To select: • All rows omit where clause • All fields, use *: SELECT * FROM … • Only unique field values: SELECT DISTINCT fieldname • Search condition: • Use comparison and logical operators • IS NULL/IS NOT NULL to match/exclude NULL values • IN/NOT IN to match set values • LIKE with wildcards % and _ to match character strings Guide to Oracle10G

22. Sorting Query Output • Use ORDER BY sort_key_field(s) • Default order is ascending, use DESC to sort descending Guide to Oracle10G

23. Using Calculations in SQL Queries • Calculations are performed by DBMS, result only sent to client • Can use arithmetic operators (+, -, *, /) • Place calculation in select clause: SELECT price * quantity FROM … • Calculations can be performed on NUMBER, DATE and INTERVAL fields only • Single-row functions: built in Oracle functions to perform calculations and manipulate retrieved data values Guide to Oracle10G

24. Oracle9i SQL Group Functions • Group functions:perform an operation on a group of queried rows and returns a single result Guide to Oracle10G

25. Group By • Use to group output by the field with duplicate values and apply group functions to the grouped data Guide to Oracle10G

26. Having • Use to place a search condition on results of group function calculations • Like “WHERE” for group functions • HAVING group_function comparison_operator value • HAVING SUM(capacity) >= 100 Guide to Oracle10G

27. Formatting Output in SQL*Plus • To change default column headings: • Specify alternate column headings: SELECT fieldname1 "heading1_text", fieldname2 "heading2_text", ... • Use an alias for column headings: SELECT fieldname1 AS alias_name1... • To change SQL*Plus line and page size settings • Select Options/Environment on menu bar • Modify linesize and pagesize to desired values Guide to Oracle10G

28. Formatting Numbers and Dates • Use to_char function with format models • TO_CHAR(field_name, 'format_model') • SELECT inv_id, TO_CHAR(inv_price, '$99,999.99') FROM inventory WHERE item_id = 1; Guide to Oracle10G

29. Lesson C Objectives • Learn how to create SQL queries that join multiple tables • Learn how to create nested SQL queries • Understand how to combine query results using set operators • Create and use database views Guide to Oracle10G

30. Joining Multiple Tables • Join: combine data from multiple database tables using foreign key references • SELECT field1, field2, ... FROM table1, table2 WHERE table1.joinfield = table2.joinfield AND search_condition(s); • If tables share field names, must prefix field in select with table name (table1.field1, table2.field1) • Join condition: part of where clause indicating how tables are related (table1.foreign_key = table2.primary key) • Search conditions can be added to join condition using AND operator Guide to Oracle10G

31. Process for DesigningComplex Inner Join Queries • Identify all of the tables involved in the query, and label: • Display fields • Join fields • Search fields • Write the query • List all display fields in the SELECT clause • List all table names in the FROM clause • List all join condition links in the WHERE clause • List all search fields in the WHERE clause Guide to Oracle10G

32. Inner Join • Join two tables based on values in one table being equal to values in another table • Also known as equality join, equijoin or natural join • Returns results only if records exist in both tables Guide to Oracle10G

33. Using a Query Design Diagram • Helpful for creating complicated queries • Can use a formula to derive actual query from diagram Guide to Oracle10G

34. Outer Joins • Returns all rows in one table and matching rows in joined table • Inner table: all rows are returned • Outer table: matching rows are returned • Outer table marked with a + in join condition • inner_table.join_field = outer_table.join_field(+) • Null values are inserted for fields in outer table that are not found Guide to Oracle10G

35. Outer Joins • Limitation of inner joins: some records may be omitted if corresponding records don’t exist in one of the tables • Example: retrieve records for all students, along with their corresponding ENROLLMENT information Guide to Oracle10G

36. Outer Joins • Student 105 (Michael Connoly) does not have any ENROLLMENT records Guide to Oracle10G

37. Outer Joins • No records retrieved for Michael: Guide to Oracle10G

38. Outer Joins • To include records in first (inner) table, even when they do not have matching records in second (outer) table, place outer join marker (+) beside outer table name in join clause Guide to Oracle10G

39. Outer Joins Guide to Oracle10G

40. Using Set Operators To Combine Query Results • Use to select data from multiple tables not connected with foreign key relationships Guide to Oracle10G

41. Set Operators • query1 OPERATOR query2; (where operator is UNION, UNION ALL, INTERSECT, or MINUS) • Both queries must have same number of select fields and same data types in same order • UNION suppresses duplicate values • UNION ALL includes duplicate values • INTERSECT takes only matching fields • MINUS takes only fields in query1 not query2 Guide to Oracle10G

42. Creating and Using Database Views • Similar to storing the result of a query in the database • Based on a source query that: • can specify a subset of a single table’s fields or records • can join multiple tables • Can be used to enforce security (user has access to view but not underlying table) Guide to Oracle10G

43. Creating and Using Database Views • Views can be updateable if: • SELECT clause contains only fieldnames, no functions or calculations • cannot contain the ORDER BY, DISTINCT, or GROUP BY clauses, group functions, or set operators • search condition cannot contain a nested query • Views are used like tables for selecting, inserting, updating and deleting data (only updatable views can be modified) Guide to Oracle10G

44. Creating and Deleting Views • CREATE OR REPLACE VIEW view_name AS source_query; • DROP VIEW viewname; Guide to Oracle10G

45. Summary • Use INSERT commands to add data • NUMBER, DATE data types can be converted to and from character strings using format models • Database changes are made within a transaction that can be committed or rolled back • Use search conditions to specify records to update, delete or select • Arithmetic, logical, grouping, and built-in Oracle functions can be used to specify search conditions and manipulate data • Query output can be formatted by modifying SELECT clause Guide to Oracle10G

46. Summary • Results from more than one table related through foreign key relationships can be combined in a join • Results from more than one unrelated table can be combined using set operators • Queries can be “saved” by creating a view • Views can be used like tables to select, insert, update and delete data Guide to Oracle10G