MS SQL Server 1

Introduction SQL is an ANSI (American National Standards Institute) standard computer language for accessing and manipulating database systems. SQL statements are used to retrieve and update data in a database.

What is SQL? Structured Query Language Communicate with databases Used to created and edit databases. Also used to create queries, forms, and reports

Working with SQL 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. Below is an example of a table called "Persons": LastName FirstName Address City Hansen Ola Timoteivn 10 Sandnes Svendson Tove Borgvn 23 Sandnes Pettersen Kari Storgt 20 Stavanger

Table Basics A Table is an object Database data is stored in Tables Each table has a unique name Columns have various attributes, such as column name and data type Rows contain records or data for the columns

Creating Tables The statement to use is create table Here is the syntax: create table “tablename” (“columnname”, “datatype”, “ columnname2”, “datatype”, “ columnname3”, “datatype”);

Example of Table creation Here is a real example: create table employee (first varchar(15), last varchar(20), age number(3), address varchar(30), city varchar(20), state varchar(20));

Creating Tables - Steps Use the command create table Follow it with the correct table name Put a parenthesis and type in the first column name Follow it with the variable type (we will list them in a minute) then a comma Continue the previous two steps until you have all your columns accounted for Then put a parenthesis to close the columnname section and add a ; after it

Creating Tables - Rules Table and column names must start with a letter They can not exceed 30 characters They can not be key words such as create, insert, select, etc.

SQL Queries With SQL, we can query a database and have a result set returned. A query like this: SELECT LastName FROM Persons Gives a result set like this: LastName Hansen Svendson Pettersen

SQL Data Manipulation Language (DML) SQL (Structured Query Language) is a syntax for executing queries. But the SQL language also includes a syntax to update, insert, and delete records. These query and update commands together form the Data Manipulation Language (DML) part of SQL: 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

SQL Data Definition Language (DDL) The Data Definition Language (DDL) part of SQL permits database tables to be created or deleted. We can also define indexes (keys), specify links between tables, and impose constraints between database tables. The most important DDL statements in SQL are: 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

Selecting Data The SELECT statement is used to select data from a table. The tabular result is stored in a result table (called the result-set). Syntax SELECT column_name(s) FROM table_name

Select few columns To select the columns named "LastName" and "FirstName", use a SELECT statement like this: SELECT LastName, FirstName FROM Persons Persons LastName FirstName Address City Hansen Ola Timoteivn 10 Sandnes Svendson Tove Borgvn 23 Sandnes Pettersen Kari Storgt 20 Stavanger Result LastName FirstName Hansen Ola Svendson Tove Pettersen Kari

Select All Columns To select all columns from the "Persons" table, use a * symbol instead of column names, like this: SELECT * FROM Persons LastName FirstName Address City Hansen Ola Timoteivn 10 Sandnes Svendson Tove Borgvn 23 Sandnes Pettersen Kari Storgt 20 Stavanger

The Result Set The result from a SQL query is stored in a result-set.

Conditions Used In Where Clause = equals > greater than < less than >= greater than or equal to <= less than or equal to <> not equal to

Using the WHERE Clause To select only the persons living in the city "Sandnes", we add a WHERE clause to the SELECT statement: SELECT * FROM Persons WHERE City='Sandnes' LastName FirstName Address City Year Hansen Ola Timoteivn 10 Sandnes 1951 Svendson Tove Borgvn 23 Sandnes 1978 Svendson Stale Kaivn 18 Sandnes 1980 Pettersen Kari Storgt 20 Stavanger 1960 LastName FirstName Address City Year Hansen Ola Timoteivn 10 Sandnes 1951 Svendson Tove Borgvn 23 Sandnes 1978 Svendson Stale Kaivn 18 Sandnes 1980

Using Quotes 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. For text values: This is correct: SELECT * FROM Persons WHERE FirstName='Tove' This is wrong: SELECT * FROM Persons WHERE FirstName=Tove

The LIKE Condition The LIKE condition is used to specify a search for a pattern in a column. Syntax SELECT column FROM table WHERE column LIKE pattern A "%" sign can be used to define wildcards (missing letters in the pattern) both before and after the pattern.

Using LIKE The following SQL statement will return persons with first names that start with an 'O': SELECT * FROM Persons WHERE FirstName LIKE 'O%' The following SQL statement will return persons with first names that end with an 'a': SELECT * FROM Persons WHERE FirstName LIKE '%a' The following SQL statement will return persons with first names that contain the pattern 'la': SELECT * FROM Persons WHERE FirstName LIKE '%la%'

The INSERT INTO Statement The INSERT INTO statement is used to insert new rows into a table. Syntax INSERT INTO table_name VALUES (value1, value2,....) You can also specify the columns for which you want to insert data: INSERT INTO table_name (column1, column2,...) VALUES (value1, value2,....)

Insert a New Row And this SQL statement: INSERT INTO Persons VALUES ('Hetland', 'Camilla', 'Hagabakka 24', 'Sandnes') LastName FirstName Address City Pettersen Kari Storgt 20 Stavanger LastName FirstName Address City Pettersen Kari Storgt 20 Stavanger Hetland Camilla Hagabakka 24 Sandnes

Insert Data in Specified Columns And This SQL statement: INSERT INTO Persons (LastName, Address) VALUES ('Rasmussen', 'Storgt 67') LastName FirstName Address City Pettersen Kari Storgt 20 Stavanger Hetland Camilla Hagabakka 24 Sandnes LastName FirstName Address City Pettersen Kari Storgt 20 Stavanger Hetland Camilla Hagabakka 24 Sandnes Rasmussen Storgt 67

Inserting Information into Tables Steps All strings should be enclosed by single quotes: 'string'** Use the keyword "insert into" followed by the tablename Then on the next line, in parenthesis, list all the columns you are inserting values for. Then on the line after, type values, then in parenthesis, put the values in the same order as the columns they belong to

The Update Statement The UPDATE statement is used to modify the data in a table. Syntax UPDATE table_name SET column_name = new_value WHERE column_name = some_value

Update one Column in a Row We want to add a first name to the person with a last name of "Rasmussen": UPDATE Person SET FirstName = 'Nina' WHERE LastName = 'Rasmussen' LastName FirstName Address City Nilsen Fred Kirkegt 56 Stavanger Rasmussen Storgt 67 LastName FirstName Address City Nilsen Fred Kirkegt 56 Stavanger Rasmussen Nina Storgt 67

The Delete Statement The DELETE statement is used to delete rows in a table. Syntax DELETE FROM table_name WHERE column_name = some_value

Delete a Row "Nina Rasmussen" is going to be deleted: DELETE FROM Person WHERE LastName = 'Rasmussen' LastName FirstName Address City Nilsen Fred Kirkegt 56 Stavanger Rasmussen Nina Stien 12 Stavanger LastName FirstName Address City Nilsen Fred Kirkegt 56 Stavanger

Delete All Rows It is possible to delete all rows in a table without deleting the table. This means that the table structure, attributes, and indexes will be intact: DELETE FROM table_name Or DELETE * FROM table_name

MS SQL Server 1

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