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    Sql Sql Document Transcript

    • SQL Introduction to SQL Atul Pant
    • Table of Contents SQL Intro .......................................................................................................................................................3 SQL Select .....................................................................................................................................................4 SQL Select Distinct ........................................................................................................................................4 SQL Where.....................................................................................................................................................4 SQL And & Or ...............................................................................................................................................5 SQL Order By ................................................................................................................................................5 SQL Insert Into ...............................................................................................................................................5 SQL Update ....................................................................................................................................................6 SQL Delete .....................................................................................................................................................6 SQL Select Top ..............................................................................................................................................6 SQL Select Top ..............................................................................................................................................7 SQL Like ........................................................................................................................................................7 SQL Wildcards ...............................................................................................................................................7 SQL IN ...........................................................................................................................................................8 SQL Between .................................................................................................................................................8 SQL Join ........................................................................................................................................................8 SQL Inner Join ...............................................................................................................................................9 SQL Left Join .................................................................................................................................................9 SQL Right Join...............................................................................................................................................9 SQL Full Join ...............................................................................................................................................10 SQL Union ...................................................................................................................................................10 SQL Select Into ............................................................................................................................................10 SQL Insert Into Select ..................................................................................................................................11 SQL Create Database ...................................................................................................................................11 SQL Create Table .........................................................................................................................................11 SQL Constraints ...........................................................................................................................................12 SQL Not Null ...............................................................................................................................................12 SQL Unique .................................................................................................................................................13 SQL Primary Key.........................................................................................................................................13 SQL Foreign Key .........................................................................................................................................14 SQL Check ...................................................................................................................................................14 SQL Default .................................................................................................................................................14 SQL Create Index .........................................................................................................................................15 SQL Drop .....................................................................................................................................................15 SQL Alter .....................................................................................................................................................15 SQL Page 1
    • SQL Null ......................................................................................................................................................16 SQL General Data Types .............................................................................................................................17 References ....................................................................................................................................................18 SQL Page 2
    • SQL Intro What is SQL?  SQL stands for Structured Query Language  SQL lets you access and manipulate databases  SQL is an ANSI (American National Standards Institute) standard What Can SQL do?  SQL can execute queries against a database  SQL can retrieve data from a database  SQL can insert records in a database  SQL can update records in a database  SQL can delete records from a database  SQL can create new databases  SQL can create new tables in a database  SQL can create stored procedures in a database  SQL can create views in a database  SQL can set permissions on tables, procedures, and views What is RDBMS?  RDBMS stands for Relational Database Management System.  RDBMS is the basis for SQL, and for all modern database systems such as MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access.  The data in RDBMS is stored in database objects called tables.  A table is a collection of related data entries and it consists of columns and rows. SQL Page 3
    • SQL Select Definition The SELECT statement is used to select data from a database. The result is stored in a result table, called the result-set. Syntax SELECT column_name FROM table_name; Example SELECT City FROM Customers; SQL Select Distinct Definition The SELECT DISTINCT statement is used to return only distinct (different) values. Syntax SELECT DISTINCT column_name,column_name FROM table_name; Example SELECT DISTINCT City FROM Customers; SQL Where Definition The WHERE clause is used to filter records. Syntax SELECT column_name, column_name FROM table_name WHERE column_name operator value; Example SELECT * FROM Customers WHERE Country='Mexico'; SQL Page 4
    • SQL And & Or The AND operator displays a record if both the first condition AND the Definition second condition are true. The OR operator displays a record if either the first condition OR the second condition is true. Syntax SELECT column_name, FROM table_name WHERE column_name (AND/OR) column_name; Example SELECT * FROM Customers WHERE Country='Germany' AND City='Berlin'; SQL Order By Definition Syntax Example The ORDER BY keyword is used to sort the result-set by one or more columns. SELECT column_name, column_name FROM table_name ORDER BY column_name, column_name ASC|DESC; SELECT * FROM Customers ORDER BY Country DESC; SQL Insert Into Definition Syntax Example SQL The INSERT INTO statement is used to insert new records in a table. INSERT INTO table_name VALUES (value1, value2, value3,...); INSERT INTO table_name (column1, column2, column3,...) VALUES (value1, value2, value3,...); INSERT INTO Customers (CustomerName, City, Country) VALUES ('Cardinal', 'Stavanger', 'Norway'); Page 5
    • SQL Update Definition Syntax Example The UPDATE statement is used to update existing records in a table. UPDATE table_name SET column1=value1, column2=value2,... WHERE some_column=some_value; UPDATE Customers SET ContactName='Alfred Schmidt', City='Hamburg' WHERE CustomerName='Alfreds Futterkiste'; SQL Delete Definition The DELETE statement is used to delete rows in a table. Syntax DELETE FROM table_name WHERE some_column=some_value; Example DELETE FROM Customers WHERE CustomerName='Alfreds Futterkiste' AND ContactName='Maria Anders'; SQL Select Top Definition Syntax Example SQL The SELECT TOP clause is used to specify the number of records to return. SELECT TOP number|percent column_name(s) FROM table_name; SELECT TOP 2 * FROM Customers; SELECT TOP 50 PERCENT * FROM Customers; Page 6
    • SQL Select Top Definition Syntax Example The SELECT TOP clause is used to specify the number of records to return. SELECT TOP number|percent column_name(s) FROM table_name; SELECT TOP 2 * FROM Customers; SELECT TOP 50 PERCENT * FROM Customers; SQL Like Definition The LIKE operator is used to search for a specified pattern in a column. Syntax SELECT column_name(s) FROM table_name WHERE column_name LIKE pattern; Example SELECT * FROM Customers WHERE City LIKE 's%'; SQL Wildcards Definition Wildcard characters are used with the SQL LIKE operator. They are used Syntax to search for data within a table. SELECT column_name(s) FROM table_name WHERE column_name LIKE pattern; SELECT * FROM Customers WHERE City LIKE 'ber%'; Example SELECT * FROM Customers WHERE City LIKE '_erlin'; SELECT * FROM Customers WHERE City LIKE '[!bsp]%'; SQL Page 7
    • SQL IN Definition The IN operator allows you to specify multiple values in a WHERE clause. Syntax SELECT column_name(s) FROM table_name WHERE column_name IN (value1,value2,...); Example SELECT * FROM Customers WHERE City IN ('Paris','London'); SQL Between Definition The BETWEEN operator selects values within a range. The values can be Syntax numbers, text, or dates. SELECT column_name(s) FROM table_name WHERE column_name BETWEEN value1 AND value2; SELECT * FROM Products WHERE Price BETWEEN 10 AND 20; Example SELECT * FROM Products WHERE Price NOT BETWEEN 10 AND 20; SELECT * FROM Orders WHERE OrderDate BETWEEN #07/04/1996# AND #07/09/1996#; SQL Join Definition Syntax Example SQL An SQL JOIN clause is used to combine rows from two or more tables, based on a common field between them. SELECT column_name(s) FROM table1 JOIN table2 ON table1.column_name=table2.column_name; SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate FROM Orders JOIN Customers ON Orders.CustomerID=Customers.CustomerID; Page 8
    • SQL Inner Join The INNER JOIN keyword selects all rows from both tables as long as Definition Syntax Example there is a match between the columns in both tables. INNER JOIN is the same as JOIN. SELECT column_name(s) FROM table1 JOIN table2 ON table1.column_name=table2.column_name; SELECT Customers.CustomerName, Orders.OrderID FROM Customers INNER JOIN Orders ON Customers.CustomerID=Orders.CustomerID ORDER BY Customers.CustomerName; SQL Left Join The LEFT JOIN keyword returns all rows from the left table (table1), Definition Syntax Example with the matching rows in the right table (table2). The result is NULL in the right side when there is no match. SELECT column_name(s) FROM table1 LEFT JOIN table2 ON table1.column_name=table2.column_name; SELECT Customers.CustomerName, Orders.OrderID FROM Customers LEFT JOIN Orders ON Customers.CustomerID=Orders.CustomerID ORDER BY Customers.CustomerName; SQL Right Join The RIGHT JOIN keyword returns all rows from the right table Definition Syntax Example SQL (table2), with the matching rows in the left table (table1). The result is NULL in the left side when there is no match. SELECT column_name(s) FROM table1 RIGHT JOIN table2 ON table1.column_name=table2.column_name; SELECT Orders.OrderID, Employees.FirstName FROM Orders RIGHT JOIN Employees ON Orders.EmployeeID=Employees.EmployeeID ORDER BY Orders.OrderID; Page 9
    • SQL Full Join Definition Syntax Example The FULL OUTER JOIN keyword returns all rows from the left table (table1) and from the right table (table2). SELECT column_name(s) FROM table1 FULL OUTER JOIN table2 ON table1.column_name=table2.column_name; SELECT Customers.CustomerName, Orders.OrderID FROM Customers FULL OUTER JOIN Orders ON Customers.CustomerID=Orders.CustomerID ORDER BY Customers.CustomerName; SQL Union Definition Syntax Example The SQL UNION operator combines the result of two or more SELECT statements. SELECT column_name(s) FROM table1 UNION SELECT column_name(s) FROM table2; SELECT City FROM Customers UNION SELECT City FROM Suppliers ORDER BY City; SQL Select Into Definition Syntax Example SQL The SELECT INTO statement selects data from one table and inserts it into a new table. SELECT * INTO newtable [IN externaldb] FROM table1; SELECT * INTO CustomersBackup2013 FROM Customers; Page 10
    • SQL Insert Into Select Definition Syntax Example The INSERT INTO SELECT statement copies data from one table and inserts it into an existing table. INSERT INTO table2 SELECT * FROM table1; INSERT INTO table2 (column_name(s)) SELECT column_name(s) FROM table1; INSERT INTO Customers (CustomerName, Country) SELECT SupplierName, Country FROM Suppliers; INSERT INTO Customers (CustomerName, Country) SELECT SupplierName, Country FROM Suppliers WHERE Country='Germany'; SQL Create Database Definition The CREATE DATABASE statement is used to create a database. Syntax CREATE DATABASE dbname; Example CREATE DATABASE my_db; SQL Create Table The CREATE TABLE statement is used to create a table in a database. Definition Syntax SQL Tables are organized into rows and columns; and each table must have a name. CREATE TABLE table_name ( column_name1 data_type(size), column_name2 data_type(size), column_name3 data_type(size), .... ); Page 11
    • Example CREATE TABLE Persons ( PersonID int, LastName varchar(255), FirstName varchar(255), Address varchar(255), City varchar(255) ); SQL Constraints Definition Syntax Example SQL constraints are used to specify rules for the data in a table. CREATE TABLE table_name ( column_name1 data_type(size) constraint_name, column_name2 data_type(size) constraint_name, column_name3 data_type(size) constraint_name, .... ); NOT NULL- Indicates that a column cannot store NULL value. UNIQUE- Ensures that each row for a column must have a unique value. PRIMARY KEY- A combination of a NOT NULL and UNIQUE. Ensures that a column (or combination of two or more columns) have an unique identity which helps to find a particular record in a table more easily and quickly. FOREIGN KEY- Ensure the referential integrity of the data in one table to match values in another table CHECK- Ensures that the value in a column meets a specific condition. DEFAULT- Specifies a default value when specified none for this column. SQL Not Null Definition Example SQL The NOT NULL constraint enforces a column to NOT accept NULL values. CREATE TABLE Persons NotNull ( P_Id int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255) ) Page 12
    • SQL Unique Definition Example The UNIQUE constraint uniquely identifies each record in a database table. CREATE TABLE Persons Unique ( P_Id int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255), UNIQUE (P_Id) ) SQL Primary Key The PRIMARY KEY constraint uniquely identifies each record in a database table. Definition Primary keys must contain unique values. A primary key column cannot contain NULL values. Each table should have a primary key, and each table can have only ONE Example SQL primary key. CREATE TABLE Persons ( P_Id int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255), PRIMARY KEY (P_Id) ) Page 13
    • SQL Foreign Key Definition Example A FOREIGN KEY in one table points to a PRIMARY KEY in another table. CREATE TABLE Orders ( O_Id int NOT NULL, OrderNo int NOT NULL, P_Id int, PRIMARY KEY (O_Id), FOREIGN KEY (P_Id) REFERENCES Persons(P_Id) ) SQL Check Definition Example The CHECK constraint is used to limit the value range that can be placed in a column. CREATE TABLE Persons ( P_Id int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255), CHECK (P_Id>0) ) SQL Default The DEFAULT constraint is used to insert a default value into a column. Definition Example SQL The default value will be added to all new records, if no other value is specified. CREATE TABLE Persons ( P_Id int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255), CHECK (P_Id>0) ) Page 14
    • SQL Create Index The CREATE INDEX statement is used to create indexes in tables. Definition Indexes allow the database application to find data fast; without reading the whole table. Syntax CREATE INDEX index_name ON table_name (column_name) Example CREATE INDEX PIndex ON Persons (LastName) SQL Drop The DROP statement is used to delete a table or database. Definition Syntax Example TRANCATE statement is when we only want to delete the data inside the table, and not the table itself. DROP TABLE table_name DROP DATABASE database_name TRUNCATE TABLE table_name DROP TABLE Person DROP DATABASE test Truncate TABLE Person SQL Alter Definition The ALTER TABLE statement is used to add, delete, or modify columns Syntax ALTER TABLE table_name ADD column_name datatype Example ALTER TABLE Persons DROP COLUMN DateOfBirth SQL in an existing table. Page 15
    • SQL Null NULL values represent missing unknown data. Definition By default, a table column can hold NULL values. Note: It is not possible to compare NULL and 0; they are not Syntax Example SQL equivalent. SELECT column_name FROM table WHERE column_name IS NULL SELECT column_name FROM table WHERE column_name IS NOT NULL SELECT LastName,FirstName,Address FROM Persons WHERE Address IS NULL SELECT LastName,FirstName,Address FROM Persons WHERE Address IS NOT NULL Page 16
    • SQL General Data Types Database Type Description CHARACTER(n) Character string. Fixed-length n VARCHAR(n) or CHARACTER VARYING(n) BINARY(n) Character string. Variable length. Maximum length n Binary string. Fixed-length n BOOLEAN Stores TRUE or FALSE values VARBINARY(n) or BINARY VARYING(n) INTEGER(p) Binary string. Variable length. Maximum length n Integer numerical (no decimal). Precision p SMALLINT Integer numerical (no decimal). Precision 5 INTEGER Integer numerical (no decimal). Precision 10 BIGINT Integer numerical (no decimal). Precision 19 DECIMAL(p,s) REAL Exact numerical, precision p, scale s. Example: decimal(5,2) is a number that has 3 digits before the decimal and 2 digits after the decimal Exact numerical, precision p, scale s. (Same as DECIMAL) Approximate numerical, mantissa precision p. A floating number in base 10 exponential notation. The size argument for this type consists of a single number specifying the minimum precision Approximate numerical, mantissa precision 7 FLOAT Approximate numerical, mantissa precision 16 DOUBLE PRECISION Approximate numerical, mantissa precision 16 DATE Stores year, month, and day values TIME Stores hour, minute, and second values TIMESTAMP Stores year, month, day, hour, minute, and second values Composed of a number of integer fields, representing a period of time, depending on the type of interval A set-length and ordered collection of elements NUMERIC(p,s) FLOAT(p) INTERVAL ARRAY MULTISET XML SQL A variable-length and unordered collection of elements Stores XML data Page 17
    • References http://www.w3schools.com/sql/ SQL Page 18