SQL is a standard language for storing, manipulating and retrieving data in databases. Our SQL tutorial will teach you how to use SQL in: MySQL, SQL Server. SQL is a standard language for accessing and manipulating databases. What is SQL? SQL stands for Structured Query Language; SQL lets you access and. SQL Statement, Syntax. AND / OR, SELECT column_name(s) FROM table_name . WHERE condition. AND|OR condition. ALTER TABLE, ALTER TABLE.
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SQL Quiz Test. Test your SQL skills at W3Schools! SQL is a standard language for accessing databases. Our SQL tutorial will teach you how to. osakeya.info 1. W3Schools SQL Tutorial Gives a result set like this: LastName Hansen Svendson Pettersen Note: Some. SQL stands for Structured Query Language. This tutorial will give you a quick start to SQL. It covers most of the topics required for a basic understanding of SQL.
Column Name Alias The syntax is: Using a Column Alias This table Persons: Using a Table Alias This table Persons: Table Employees: We have to perform a join. Tables in a database can be related to each other with keys. A primary key is a column with a unique value for each row. The purpose is to bind data together, across tables, without repeating all of the data in every table. When you look at the example tables below, notice that: Example Who has ordered a product, and what did they order?
Name, Orders. If there are rows in Employees that do not have matches in Orders, those rows will not be listed. If there are rows in Employees that do not have matches in Orders, those rows also will be listed. If there had been any rows in Orders that did not have matches in Employees, those rows also would have been listed.
This command cannot be used to list all employees in Norway and USA.
In the example above we have two employees with equal names, and only one of them is listed. Example This example demonstrates how you can create a table named "Person", with four columns.
The table below contains the most common data types in SQL: Data Type integer size int size smallint size tinyint size decimal size,d numeric size,d char size varchar size Description Hold integers only.
The maximum number of digits are specified in parenthesis. Hold numbers with fractions. The maximum number of digits are specified in "size".
The maximum number of digits to the right of the decimal is specified in "d". Holds a fixed length string can contain letters, numbers, and special characters. The fixed size is specified in parenthesis. Holds a variable length string can contain letters, numbers, and special characters. The maximum size is specified in parenthesis.
It is possible to create an index on one or more columns of a table, and each index is given a name. The users cannot see the indexes, they are just used to speed up queries. Updating a table containing indexes takes more time than updating a table without, this is because the indexes also need an update.
So, it is a good idea to create indexes only on columns that are often used for a search. A Unique Index Creates a unique index on a table. A unique index means that two rows cannot have the same index value.
A Simple Index Creates a simple index on a table. The basic types of functions are: What is a View? A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database. The database design and structure will NOT be affected by the functions, where, or join statements in a view. The database does not store the view data! Using Views A view could be used from inside a query, a stored procedure, or from inside another view.
By adding functions, joins, etc. The sample database Northwind has some views installed by default. The view "Current Product List" lists all active products products that are not discontinued from the Products table. The view is created with the following SQL: Note that this view select its data from another view called "Product Sales for ": Now we want to see the total sale only for the category "Beverages": Kiran Leo.
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