{"id":44411,"date":"2018-12-10T10:30:16","date_gmt":"2018-12-10T05:00:16","guid":{"rendered":"https:\/\/data-flair.training\/blogs\/?p=44411"},"modified":"2021-03-11T21:22:06","modified_gmt":"2021-03-11T15:52:06","slug":"sql-statements","status":"publish","type":"post","link":"https:\/\/data-flair.training\/blogs\/sql-statements\/","title":{"rendered":"Easy Way To Understand SQL Statements and Its Uses"},"content":{"rendered":"

In this tutorial, we will learn about the various statements available for use in SQL. With this tutorial, we will dive deep into the world of SQL Statements with examples wherever required.<\/p>\n

What are the SQL Statements?<\/h3>\n

SQL statements update, manipulate and maintain the data in a database, or retrieve data from a database. Some of the common statements that we use are DDL and DML statements.<\/p>\n

The basic SELECT, UPDATE and DELETE statements are used extensively by developers in integration and deployment of even industry-level applications.<\/p>\n

The CRUD operations which we perform extensively are also done using the SQL statements.<\/p>\n

Demo Database<\/h4>\n

Let us know have a look at our demo database – DataFlair<\/strong>.
\nQuery:\u00a0<\/strong><\/p>\n

SELECT * FROM DataFlair;\r\n<\/pre>\n
Output:<\/strong><\/p>\n
\"SQL<\/a><\/p>\n
Uses of SQL Statements<\/h3>\n
Some of the uses of SQL statements are as follows:<\/p>\n
    \n
  1. Allow us to perform CRUD operations.<\/li>\n
  2. Provides us with the flexibility to maintain and create the database.<\/li>\n
  3. DML statements help us to manipulate the data.<\/li>\n
  4. DDL statements help us to declare the data.<\/li>\n<\/ol>\n
    Types of SQL Statements<\/h3>\n
    SQL works by running the commands provided by the user. We can divide the SQL commands into five distinctions based on the functionality they provide:<\/p>\n
    1. DDL (Data Definition Language)<\/h4>\n
    DDL is used to define the structure or schema of the database and to specify additional properties of the data.<\/p>\n
    These statements define the implementation of the schema and are mostly hidden from the user, also the data stored in the database is made to follow certain constraints.<\/p>\n
    Some of the DDL commands are as follows :<\/p>\n
    a. Create<\/strong><\/p>\n
    To create objects in the database<\/p>\n
    CREATE TABLE tableName(\r\ncol1 datatype,\r\ncol2  datatype,\r\ncol3  datatype\u2026..);\r\n<\/pre>\n
    Example: Let us now see the query to create our DataFlair database.<\/p>\n
    CREATE TABLE DataFlair(\r\nemp_id varchar(5),\r\nname varchar(50),\r\nlocation varchar(50),\r\nexperience int);\r\n<\/pre>\n
    Output:<\/strong><\/p>\n
    \"Create<\/a><\/p>\n
    2. Alter in SQL<\/strong><\/p>\n
    Alters the structure of the database<\/p>\n
    Syntax<\/strong><\/p>\n
    ALTER TABLE tableName\r\nADD columnName datatype;\r\n<\/pre>\n
    Example:<\/strong><\/p>\n
    ALTER TABLE DataFlair\r\nADD emp_id varchar(5);\r\n<\/pre>\n
    Output:<\/strong><\/p>\n
    \"alter<\/a><\/p>\n
    3. Drop in SQL<\/strong><\/p>\n
    Delete objects from the database
    \nSyntax:<\/strong><\/p>\n
    DROP TABLE tableName;\r\n<\/pre>\n
    Example: Let us now see how to drop the table DataFlair.
    \nQuery:<\/strong><\/p>\n
    DROP TABLE DataFlair;\r\n<\/pre>\n
    Output:<\/strong><\/p>\n
    \"Drop<\/a><\/p>\n
    4. Truncate in SQL<\/strong><\/p>\n
    Deletes all the data stored in a table
    \nSyntax:<\/strong><\/p>\n
    TRUNCATE TABLE  tableName;\r\n<\/pre>\n
    Example: Let us now see how to truncate a table.
    \nQuery:<\/strong><\/p>\n
    TRUNCATE TABLE  DataFlair;\r\n<\/pre>\n
    Output:<\/strong><\/p>\n
    \"Truncate<\/a><\/p>\n
    B. DML(Data Manipulation Language)<\/h4>\n
    DML is used for managing data contained in the schema objects. DML\u2019s can be divided into two subtypes :<\/p>\n