Sql basics


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Sql basics

  1. 1. Genesis Omo 1
  2. 2.  an acronym for Structured Query Language forms the backbone of most modern database systems the language of databases a standard programming language for querying and modifying data and managing databases. a standard computer language for accessing and manipulating databases. 2
  3. 3.  SQL allows you to access a database SQL is an ANSI standard computer language SQL can execute queries against a database SQL can retrieve data from a database SQL can insert new records in a database SQL can delete records from a database SQL can update records 3
  4. 4.  The first version of SQL, initially called SEQUEL, was developed at IBM by Chamberlin and Boyce in the early 1970s. later formally standardized by the American National Standards Institute (ANSI) in 1986. The first non-commercial non-SQL RDBMS, INGRES, was developed in 1974 at the U.C. Berkely. Ingres implemented a query language known as QUEL, which was later supplanted in the marketplace by SQL. In the late 1970s, Relational Software, Inc. (now Oracle Corp.) saw the potential of the concepts described by Codd, Chamberlin, and Boyce and developed their own SQL-based RDBMS. 4
  5. 5.  Statements which may have a persistent effect on schemas and data, or which may control transactions, program flow, connections, sessions, or diagnostics. Queries which retrieve data based on specific criteria. Expressions which can produce either scalar values or tables consisting of columns and rows of data. Predicates which specify conditions that can be evaluated to SQL three-valued logic (3VL). 5
  6. 6.  Clauses which are (in some cases optional) constituent components of statements and queries. Whitespace is generally ignored in SQL statements and queries, making it easier to format SQL code for readability. SQL statements also include the semicolon (";") statement terminator. Though not required on every platform, it is defined as a standard part of the SQL grammar. 6
  7. 7. • A database most often contains one or more tables.• Each table is identified by a name (e.g. "Customers" or "Orders").Tables contain records (rows) with data. 7
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  9. 9.  Table: Enrol  Class_Code  Stu_Num Table:  Enroll_Grade Student_Info  Table: Class • Stu_Num  Class_Code • Stu_LName  Crs_Cde • Stu_Fname  Class_Section  Class_Room • Stu_MName  Pro_Num • Stu_Bdate • Stu_Hrs  Table: Course • Stu_Class  Crs_Code  Dept_Code • Stu_GPA  Crs_Description • Stu_Transfer  Crs_Credit • Dept_Code • Stu_Phone 9
  10. 10.  With SQL, we can query a database and have a result set returned. SELECT LastName FROM Persons 10
  11. 11.  SQL (Structured Query Language) is a syntax for executing queries. SQL language also includes a syntax to update, insert, and delete records. 11
  12. 12. • SELECT - extracts data from a database table• UPDATE - updates data in a database table• DELETE - deletes data from a database table• INSERT INTO - inserts new data into a database table 12
  13. 13.  Data Definition Language (DDL) part of SQL permits database tables to be created or deleted. Define indexes (keys), specify links between tables, and impose constraints between database tables. 13
  14. 14. • CREATE TABLE - creates a new database table• ALTER TABLE - alters (changes) a database table• DROP TABLE - deletes a database table• CREATE INDEX - creates an index (search key)• DROP INDEX - deletes an index 14
  15. 15.  SELECT statement is used to select data from a table. The tabular result is stored in a result table (called the resultset). Syntax SELECT column_name(s) FROM table_name 15
  16. 16.  Toselect the content of columns named "LastName" and "FirstName", from the database table called "Persons", use a SELECT statement like this: SELECT LastName,FirstName FROM Persons 16
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  18. 18.  Toselect all columns from the "Persons" table, use a * symbol instead of column names, like this: SELECT * FROM Persons 18
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  20. 20.  The DISTINCT keyword is used to return only distinct (different) values. The SELECT statement returns information from table columns. But what if we only want to select distinct elements? With SQL, all we need to do is to add a DISTINCT keyword to the SELECT statement:Syntax :SELECT DISTINCT column_name(s)FROM table_name 20
  21. 21.  Toselect ALL values from the column named "Company" we use a SELECT statement like this: SELECT Company FROM Orders 21
  22. 22.  Semicolon is the standard way to separate each SQL statement in database systems that allow more than one SQL statement to be executed in the same call to the server. 22
  23. 23.  DISTINCT keyword is used to return only distinct (different) values. SELECT statement returns information from table columns. But what if we only want to select distinct elements? Syntax SELECT DISTINCT column_name(s) FROM table_name 23
  24. 24.  Toselect ALL values from the column named "Company" we use a SELECT statement like this: SELECT Company FROM Orders 24
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  26. 26.  SELECT DISTINCT Company FROM Orders 26
  27. 27.  To conditionally select data from a table, a WHERE clause can be added to the SELECT statement. Syntax SELECT column FROM table WHERE column operator value 27
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  29. 29.  Toselect only the persons living in the city "Sandnes", we add a WHERE clause to the SELECT statement: 29
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  31. 31.  Note that we have used single quotes around the conditional values in the examples. SQL uses single quotes around text values (most database systems will also accept double quotes). Numeric values should not be enclosed in quotes. 31
  32. 32.  Thisis correct: SELECT * FROM Persons WHEREFirstName=Tove This is wrong:SELECT * FROM Persons WHEREFirstName=Tove 32
  33. 33.  This is correct: SELECT * FROM Persons WHEREYear>1965 Thisis wrong: SELECT * FROM Persons WHEREYear>1965 33
  34. 34.  TheLIKE condition is used to specify a search for a pattern in a column. Syntax SELECT column FROM table WHERE column LIKE patternA "%" sign can be used to define wildcards(missing letters in the pattern) both beforeand after the pattern. 34
  35. 35.  The following SQL statement will return persons with first names that start with an O: SELECT * FROM Persons WHERE FirstName LIKE O%‘ SELECT * FROM Persons WHERE FirstName LIKE %a‘ SELECT * FROM Persons WHERE FirstName LIKE %la% 35
  36. 36.  INSERTINTO statement is used to insert new rows into a table. Syntax INSERT INTO table_name VALUES (value1, value2,....) INSERT INTO table_name (column1,column2,...) VALUES (value1, value2,....) 36
  37. 37.  This "Persons" table: 37
  38. 38. INSERT INTO Persons VALUES (Hetland, Camilla,Hagabakka 24, Sandnes) 38
  39. 39. Insert Data in Specified ColumnsThis "Persons" table: 39
  40. 40. Tables: Customer Invoice Line ProductsIdentify the different fields pertable Inv_Number: inv,line  Line_Price: line Cus_Code: cus,inv  Inv_Date: inv Prod_Code: prod,line Cus_Lname: cus  Prod_Descript: prod Cus_Fname: cus  Prod_Price: prod Cus_Initial: cus  Prod_On_Hand: prod Cus_Areacode: cus Cus_Phone: cus  Vend_Code:prod Line_Units: line, prod 40