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Quick Tutorialspoint. This tutorial will give you a quick start to SQL. It covers most of the topics required for a basic understanding of SQL and to get a feel of how it works. Tutorial Sweetadult. Online Cityloading. This site is like a library, you could find million book here by using search box. Deletion Hcoe. SQL is a language of database, it includes database creation, deletion, fetching rows and modifying rows etc. W3Schools Thecrazyprogrammer. Fortunately, I have found a great solution to this problem.
So in this article, I am sharing the link to download W3Schools offline version for absolutely free. W3schools Getallcourses. Standard Teacher-faq. Postgres Xpcourse. SQL is a standard language for storing, manipulating and retrieving data in databases. This means that the table structure, attributes, and indexes will be intact:.
Example To display the companies in alphabetical order AND the ordernumbers in numerical order:. Example To display the companies in reverse alphabetical order AND the ordernumbers in numerical order:. Example Use OR to display each person with the first name equal to "Tove", or the last name equal to "Svendson":.
AND operator selects a range of data between two values. These values can be numbers, text, or dates. Example 1 To display the persons alphabetically between and including "Hansen" and exclusive "Pettersen", use the following SQL:. AND operator is treated differently in different databases. AND only selects fields that are between and excluding the test values. AND selects fields that are between and including the test values. AND selects fields between the test values, including the first test value and excluding the last test value.
AND operator! Example 2 To display the persons outside the range used in the previous example, use the NOT operator:.
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:. Referring to Two Tables We can select data from two tables by referring to two tables, like this:.
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. 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. Create Index Indices are created in an existing table to locate rows more quickly and efficiently. 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. Note: 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. Delete a Table or Database To delete a table the table structure, attributes, and indexes will also be deleted :.
Truncate a Table What if we only want to get rid of the data inside a table, and not the table itself? The basic types of functions are:. Aggregate functions Aggregate functions operate against a collection of values, but return a single value.
Scalar functions Scalar functions operate against a single value, and return a single value based on the input value. The above code is invalid because the column returned is not part of an aggregate. Make a Backup Copy The following example makes a backup copy of the "Persons" table:. 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. Note: The database design and structure will NOT be affected by the functions, where, or join statements in a view.
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":.
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