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SQL-Basics

SQL Basics learn by doing

SQL (pronounced "ess-que-el") is a standard language for accessing databases.

This is a list of basic SQL commands that will also include live examples using MS SQL Server and also instructions on how to setup your own MS SQL Server environment.

Examples coming soon

Microsoft SQL Server 2016 editions

SQL Statements – part 1

SELECT

FROM

WHERE

ORDER BY

BETWEEN

SELECT

  • SELECT -The SELECT statement is used to select data from a database

  • FROM - The FROM clause is used to list the tables and any joins required for the SQL statement

SELECT * FROM table_name;

Example:

WHERE
  • WHERE - The WHERE clause is used to filter the results and apply conditions in a SELECT, INSERT, UPDATE, or DELETE statement
SELECT column_name,column_name
FROM table_name
WHERE column_name operator value;

Example:

ORDER BY
  • ORDER BY - The ORDER BY keyword sorts the records in ascending order by default. To sort the records in a descending order, you can use the DESC keyword.
SELECT column_name, column_name
FROM table_name
ORDER BY column_name ASC|DESC, column_name ASC|DESC;

Example:

BETWEEN
  • BETWEEN - The BETWEEN operator selects values within a range. The values can be numbers, text, or dates.
SELECT column_name(s)
FROM table_name
WHERE column_name BETWEEN value1 AND value2;

Example:

SQL Statements – part 2

INNER JOIN

ON

INNER JOIN

  • INNER JOIN - The INNER JOIN keyword selects all rows from both tables as long as there is a match between the columns in both tables.
  • ON - Is part of the INNER JOINS
SELECT column_name(s) FROM table1
INNER JOIN table2
ON table1.column_name=table2.column_name;

Example:

SQL Statements – part 3

GROUP BY

HAVING

GROUP BY
  • GROUP BY - The GROUP BY statement is used in conjunction with the aggregate functions to group the result-set by one or more columns.
SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name;

/*
SQL aggregate functions return a single value, calculated from values in a column.

Useful aggregate functions:

AVG() - Returns the average value
COUNT() - Returns the number of rows
FIRST() - Returns the first value
LAST() - Returns the last value
MAX() - Returns the largest value
MIN() - Returns the smallest value
SUM() - Returns the sum
*/

Example:

HAVING
  • HAVING - The HAVING clause was added to SQL because the WHERE keyword could not be used with aggregate functions.
SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name
HAVING aggregate_function(column_name) operator value;

Example:

SQL Statements – part 4

DISTINCT

MAX

MIN

SUM

DISTINCT
  • DISTINCT - The SELECT DISTINCT statement is used to return only distinct (different) values.
SELECT DISTINCT column_name,column_name
FROM table_name;

Example:

MAX
  • MAX - The MAX() function returns the largest value of the selected column.
SELECT MAX(column_name) FROM table_name;

Example:

MIN
  • MIN - The MIN() function returns the smallest value of the selected column.
SELECT MIN(column_name) FROM table_name;

Example:

SUM
  • SUM - The SUM() function returns the total sum of a numeric column.
SELECT SUM(column_name) FROM table_name;

Example:

Creating a New Database - Part 5

This is an example on how to create a new database using MS SQL SERVER

Screencast will be coming soon

Steps:

Step 1:

  • On Object Explorer click on Databases right click and select New Database…

Step 2:

  • A window will pop up you will need to input/enter a new Database name: example New_DB_Test then press the OK button

Finally the new Database has been created

Example:

SQL Statements – part 6

CREATE TABLE

INSERT INTO

DELETE

UPDATE

SELECT INTO

ALTER TABLE

CREATE TABLE
  • CREATE TABLE - The CREATE TABLE statement is used to create a table in a database.
CREATE TABLE table_name
(
column_name1 data_type(size),
column_name2 data_type(size),
column_name3 data_type(size),
);

Example:

Screenshots coming soons

Creating a table

Right click on the Database you are wanting to create the new table for, example: New_DB_Test then select New Query

Within the query dashboard Input/enter the table information then press Execute the table will then be created.

CREATE TABLE Persons
(
PersonID int,
LastName varchar(255),
FirstName varchar(255),
Address varchar(255),
City varchar(255)
);
INSERT INTO
  • INSERT INTO - The INSERT INTO statement is used to insert new records in a table.
INSERT INTO table_name (column1,column2,column3,...)
VALUES (value1,value2,value3,...);

Example:

This example is using the Persons table that was mentioned before

INSERT INTO Persons (PersonID, LastName, FirstName, Address, City)
VALUES('1', 'Smith', 'John', '123 Main St.', 'Fort Worth');
DELETE
  • DELETE - The DELETE statement is used to delete rows in a table.
DELETE FROM table_name
WHERE some_column=some_value;

Example:

Suppose we wanted to delete row 2 from the Persons table you would input the following

DELETE FROM Persons
WHERE PersonID=2;
UPDATE
  • UPDATE - The UPDATE statement is used to update records in a table.
UPDATE table_name
SET column1=value1,column2=value2,...
WHERE some_column=some_value;

Example:

We will update row 2 City from Fort Worth to Dallas using the Persons table

UPDATE Persons
SET City = 'Dallas'
WHERE City = 'Fort Worth'

-If you are wanting to update the specific table columns you can do so without the WHERE Clause and those specified columns on the table will be updated.

UPDATE table_name
SET column1=value1,column2=value2,...
SELECT INTO
  • SELECT INTO - The SELECT INTO statement copies data from one table and inserts it into a new table.
/*
We can copy all columns into the new table:
*/
SELECT *
INTO newtable [IN externaldb]
FROM table1;
/*
Or we can copy only the columns we want into the new table:
*/
SELECT column_name(s)
INTO newtable [IN externaldb]
FROM table1;
/*
The new table will be created with the column-names and types as defined in the SELECT statement. 
You can apply new names using the AS clause.
*/

Example:

We will add data from Persons table into a new table; Employees

/*
Database:
       New_DB_Test
Tables:
       Persons
       Employees
*/
SELECT FirstName, LastName, PersonID 
INTO Employees
FROM Persons;
ALTER TABLE
  • ALTER TABLE - The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.
/*
To add a column in a table, use the following syntax:
*/
ALTER TABLE table_name
ADD column_name datatype
/*
To delete a column in a table, use the following syntax (some database systems don't allow deleting a column):
*/
ALTER TABLE table_name
DROP COLUMN column_name

Example:

JobTitle was added to the Employees table

ALTER TABLE Employees
ADD JobTitle varchar(255)

If we want to add job titles to the Employees table

UPDATE table_name
SET column1 = value1, column2 = value2...., columnN = valueN
WHERE [condition];

UPDATE Employees
SET JobTitle = 'CEO'
WHERE PersonID = 1;




Microsoft SQL Server Management Studio


Overview:
This is a screencast of the Microsoft SQL Server Management Studio


Screencast will be coming soon




SQL Stored Procedure


Create procedure <procedure_Name> 
As 
Begin 
<SQL Statement> 
End 
Go


/*
 Create Procedure 
*/
Create procedure GetIDInfo 
As 
Begin 
SELECT * FROM IDInfo
End 
Go


/*
 Alter the  procedure
*/
ALTER procedure GetIDInfo 
As 
Begin 
SELECT Top 20 * FROM IDInfo
End 
Go


/*
Drop procedure
*/
DROP PROCEDURE GetIDInfo 
GO


/*
Stored Procedure with Parameters 
*/
CREATE PROCEDURE Get_IDInfo
@NumID varchar(50)
AS
SELECT ID 
FROM IDInfo
WHERE ID = @NumID 
GO


/*
Executing Stored procedures with Parameters
This execution procedure is an example 
*/
EXEC Get_IDInfo 1




References


W3 Schools - SQL Tutorial


Tech on the Net