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Introduction to Sql

INTRODUCTION TO DBMS

Database

A database is something which stores the information (processed data).

DBMS

DBMS stands for Database Management System .The DBMS manages the data and arrange it in an organized form i.e. in the form of tables. The DBMS can Create, Insert, Modify, Delete and perform other operations on the Tables and Columns the Database we are operating on.

Databases stores data in the Forms of Tables --> Columns and Rows.

Eg. Student RECORD

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Sno.| NAME | CLASS | CONTACT | ADDRESS | EMAIL | 1 |abhi | 1 | 2260143 | JANAKPURI EAST | ABH1@gmail.com | 2 |Ben | 1 | 1100192 | KALKAJI ext. | ben@gmail.com |

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The above data is a structured data in the form of rows and columns. So in order to extract,alter or modify data from the above table we use some query and these queries are considered as STRUCTURED QUERIED LANGUAGE or SQL.

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SQL BASICS

SQL is the language in which a Database can communicate by creating , modifying or inserting any type of data. Structured Query Language works on the basis of queries. Select * from table_name; Queries

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1. Insert ========= Insert into <table_name>(Columns_name) values();

   INSERT INTO information (Name, Age, Gender, Address) VALUES ('aman', '25', 'M', 'Vikram NAGAR');

2. Select ========= Select * from <table_name>;

   • ---> everything Select * from information;

3. Update ========= Update <table_name> set where ;

   UPDATE information set Age=30 WHERE Name="Aman"

4. Where ======== Condition clause Select * from information where name like "A%"

5. Delete ========= Delete from <table_name> where ;

   Delete from information where name="Aman"

6. Create ========= create table <table_name>(Column_name data_type(length));

   CREATE TABLE info(name text(30),salary int(6));

7. Order By =========== Is used fir arranging data either in ascending order or in descending order. select * from <table_name> order by name; select * from staff order by age;

8. group by =========== It is used for making a group

   select * from table_name group by gender;

9. Union ======== Used fro combining data of two different tables. Column number in both the table must be equal. null

10. Information_schema ====================== It is a meta tables which stores only meta data ---> only table names and column names, but it will not store the data inside the column name or table.

    If I want to see only the table name ---> Information_schema.tables

    If I want to see the column name --> Information_schema.columns