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SQL and Client Applications

SQL and Client Applications. University of California, Berkeley School of Information Management and Systems SIMS 257: Database Management. Lecture Outline. Review Relational Operations Relational Algebra Relational Calculus Introduction to SQL Introduction to SQL (continued)

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SQL and Client Applications

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  1. SQL and Client Applications University of California, Berkeley School of Information Management and Systems SIMS 257: Database Management

  2. Lecture Outline • Review • Relational Operations • Relational Algebra • Relational Calculus • Introduction to SQL • Introduction to SQL (continued) • Application Development in Access

  3. Lecture Outline • Review • Relational Operations • Relational Algebra • Relational Calculus • Introduction to SQL • Introduction to SQL (continued) • Application Development in Access

  4. Relational Algebra Operations • Select • Project • Product • Union • Intersect • Difference • Join • Divide

  5. Select • Extracts specified tuples (rows) from a specified relation (table).

  6. Project • Extracts specified attributes(columns) from a specified relation.

  7. Join A1 B1 A2 B1 A3 B2 B1 C1 B2 C2 B3 C3 A1 B1 C1 A2 B1 C1 A3 B2 C2 • Builds a relation from two specified relations consisting of all possible concatenated pairs, one from each of the two relations, such that in each pair the two tuples satisfy some condition. (E.g., equal values in a given col.) (Natural or Inner) Join

  8. Outer Join B1 C1 B2 C2 B3 C3 Outer Join A1 B1 C1 A2 B1 C1 A3 B2 C2 A4 * * A1 B1 A2 B1 A3 B2 A4 B7 • Outer Joins are similar to PRODUCT -- but will leave NULLs for any row in the first table with no corresponding rows in the second.

  9. Join Items

  10. Relational Algebra • What is the name of the customer who ordered Large Red Widgets? • Select “large Red Widgets” from Part as temp1 • Join temp1 with Line-item on Part # as temp2 • Join temp2 with Invoice on Invoice # as temp3 • Join temp3 with customer on cust # as temp4 • Project Name from temp4

  11. Relational Calculus • Relational Algebra provides a set of explicit operations (select, project, join, etc) that can be used to build some desired relation from the database. • Relational Calculus provides a notation for formulating the definition of that desired relation in terms of the relations in the database without explicitly stating the operations to be performed • SQL is based on the relational calculus.

  12. SQL - History • Structured Query Language • SEQUEL from IBM San Jose • ANSI 1992 Standard is the version used by most DBMS today (SQL92) • Basic language is standardized across relational DBMSs. Each system may have proprietary extensions to standard.

  13. Lecture Outline • Review • Relational Operations • Relational Algebra • Relational Calculus • Introduction to SQL • Introduction to SQL (continued) • Application Development in Access

  14. SQL Uses • Database Definition and Querying • Can be used as an interactive query language • Can be imbedded in programs • Relational Calculus combines Select, Project and Join operations in a single command: SELECT

  15. SELECT • Syntax: • SELECT [DISTINCT] attr1, attr2,…, attr3 FROM rel1 r1, rel2 r2,… rel3 r3 WHERE condition1 {AND | OR} condition2 ORDER BY attr1 [DESC], attr3 [DESC]

  16. SELECT • Syntax: • SELECT a.author, b.title FROM authors a, bibfile b, au_bib c WHERE a.AU_ID = c.AU_ID and c.accno = b.accno ORDER BY a.author ; • Examples in Access...

  17. SELECT Conditions • = equal to a particular value • >= greater than or equal to a particular value • > greater than a particular value • <= less than or equal to a particular value • <> not equal to a particular value • LIKE “*term*” (may be other wild cards in other systems) • IN (“opt1”, “opt2”,…,”optn”) • BETWEEN val1 AND val2 • IS NULL

  18. Relational Algebra Selection using SELECT • Syntax: • SELECT * FROM rel1 WHERE condition1 {AND | OR} condition2;

  19. Relational Algebra Projection using SELECT • Syntax: • SELECT [DISTINCT] attr1, attr2,…, attr3 FROM rel1 r1, rel2 r2,… rel3 r3;

  20. Relational Algebra Join using SELECT • Syntax: • SELECT * FROM rel1 r1, rel2 r2 WHERE r1.linkattr = r2.linkattr ;

  21. Sorting • SELECT BIOLIFE.[Common Name], BIOLIFE.[Length (cm)] FROM BIOLIFE ORDER BY BIOLIFE.[Length (cm)] DESC; Note: the square brackets are not part of the standard, But are used in Access for names with embedded blanks

  22. Subqueries • SELECT SITES.[Site Name], SITES.[Destination no] FROM SITES WHERE sites.[Destination no] IN (SELECT [Destination no] from DEST where [avg temp (f)] >= 78); • Can be used as a form of JOIN.

  23. Aggregate Functions • Count • Avg • SUM • MAX • MIN • Others may be available in different systems

  24. Using Aggregate functions • SELECT attr1, Sum(attr2) AS name FROM tab1, tab2 ... GROUP BY attr1, attr3 HAVING condition;

  25. Using an Aggregate Function • SELECT DIVECUST.Name, Sum([Price]*[qty]) AS Total FROM (DIVECUST INNER JOIN DIVEORDS ON DIVECUST.[Customer No] = DIVEORDS.[Customer No]) INNER JOIN DIVEITEM ON DIVEORDS.[Order No] = DIVEITEM.[Order No] GROUP BY DIVECUST.Name HAVING (((DIVECUST.Name) Like "*Jazdzewski"));

  26. GROUP BY • SELECT DEST.[Destination Name], Count(*) AS Expr1 FROM DEST INNER JOIN DIVEORDS ON DEST.[Destination Name] = DIVEORDS.Destination GROUP BY DEST.[Destination Name] HAVING ((Count(*))>1); • Provides a list of Destinations with the number of orders going to that destination

  27. Lecture Outline • Review • Relational Operations • Relational Algebra • Relational Calculus • Introduction to SQL • Introduction to SQL (continued) • Application Development in Access

  28. CREATE Table • CREATE TABLE table-name (attr1 attr-type PRIMARYKEY, attr2 attr-type,…,attrN attr-type); • Adds a new table with the specified attributes (and types) to the database.

  29. Access Data Types • Numeric (1, 2, 4, 8 bytes, fixed or float) • Text (255 max) • Memo (64000 max) • Date/Time (8 bytes) • Currency (8 bytes, 15 digits + 4 digits decimal) • Autonumber (4 bytes) • Yes/No (1 bit) • OLE (limited only by disk space) • Hyperlinks (up to 64000 chars)

  30. Access Numeric types • Byte • Stores numbers from 0 to 255 (no fractions). 1 byte • Integer • Stores numbers from –32,768 to 32,767 (no fractions) 2 bytes • Long Integer(Default) • Stores numbers from –2,147,483,648 to 2,147,483,647 (no fractions). 4 bytes • Single • Stores numbers from -3.402823E38 to –1.401298E–45 for negative values and from 1.401298E–45 to 3.402823E38 for positive values. 4 bytes • Double • Stores numbers from –1.79769313486231E308 to –4.94065645841247E–324 for negative values and from 1.79769313486231E308 to 4.94065645841247E–324 for positive values. 15 8 bytes • Replication ID • Globally unique identifier (GUID) N/A 16 bytes

  31. Oracle Data Types • CHAR (size) -- max 2000 • VARCHAR2(size) -- up to 4000 • DATE • DECIMAL, FLOAT, INTEGER, INTEGER(s), SMALLINT, NUMBER, NUMBER(size,d) • All numbers internally in same format… • LONG, LONG RAW, LONG VARCHAR • up to 2 Gb -- only one per table • BLOB, CLOB, NCLOB -- up to 4 Gb • BFILE -- file pointer to binary OS file

  32. Creating a new table from existing tables • Syntax: • SELECT [DISTINCT] attr1, attr2,…, attr3 INTO newtablename FROM rel1 r1, rel2 r2,… rel3 r3 WHERE condition1 {AND | OR} condition2 ORDER BY attr1 [DESC], attr3 [DESC]

  33. ALTER Table • ALTER TABLE table-name ADD COLUMN attr1 attr-type; • … DROP COLUMN attr1; • Adds a new column to an existing database table.

  34. INSERT • INSERT INTO table-name (attr1, attr4, attr5,…, attrK) VALUES (“val1”, val4, val5,…, “valK”); • Adds a new row(s) to a table. • INSERT INTO table-name (attr1, attr4, attr5,…, attrK) VALUES SELECT ...

  35. DELETE • DELETE FROM table-name WHERE <where clause>; • Removes rows from a table.

  36. UPDATE • UPDATE tablename SET attr1=newval, attr2 = newval2 WHERE <where clause>; • changes values in existing rows in a table (those that match the WHERE clause).

  37. DROP Table • DROP TABLE tablename; • Removes a table from the database.

  38. CREATE INDEX • CREATE [ UNIQUE ] INDEX indexname ON tablename (attr1 [ASC|DESC][, attr2 [ASC|DESC], ...]) [WITH { PRIMARY | DISALLOW NULL | IGNORE NULL }]

  39. Lecture Outline • Review • Relational Operations • Relational Algebra • Relational Calculus • Introduction to SQL • Introduction to SQL (continued) • Application Development in Access

  40. Database Applications • Generally, end-users of database data probably do not want to learn SQL in order to access the information in the database • Instead, they would prefer to use a familiar PC or Web interface that uses the graphical conventions and behaviors that they are familiar with • Today we will look at PC –style client applications using systems like Access • Next time we will look at Web-based systems

  41. Query-by-Example • QBE was developed in the 1970s as a simpler to use interface for IBM mainframe databases • In QBE the user puts parts of what they want to get from the database into a form similar to what the output will look like • The Query Design View in Access is an example of QBE

  42. Access Usability Hierarchy API VBA MACROS Functions/Expressions Objects – Tables, queries Forms, Reports From McFadden Chap. 10

  43. Examples • Access OBJECT level • QBE querying • Building Application interfaces • User wants “point and click” and forms to fill in, not a Query editing screen or wizard • How to build them • Drag and drop as in Access • Programming Languages • 4th Generation languages (more on these later)

  44. The MS JET Database Engine Database app Database app Visual Basic Access Excel Word Visual Basic for Applications (VBA) Host Languages for the Jet DBMS Data Access Objects (DAO) Includes DDL and DML Jet Query Engine Internal ISAM Replication Engine Jet Database Engine (Jet DBMS) Database Adapted from Roman, “Access Database Design and Programming”

  45. Using Access for Applications • Forms • Reports • Macros • VBA programming • Application framework • HTML Pages

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