INTRODUCTION
In this blog. let’s see about SQL basic queries and using queries how to create table and insert values in the table and how to alter, delete, update values in the table.
CREATE DATABASE
It is used to create a new database.
Syntax
CREATE DATABASE database_name;
Example
CREATE DATABASE college;
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DROP DATABASE
It is used to delete the database.
Syntax
DROP DATABASE database_name;
OR
DROP SCHEMA database_name; --- using SCHEMA keyword to delete the database --
Example
DROP DATABASE college;
IF EXISTS
To prevent error if database is not found.
For example
DROP SCHEMA IF EXISTS college;
If we deleted the database and we use IF EXISTS to delete the database it shows a warning message. If the database is not deleted we want to delete the database using the IF EXISTS to delete the database.
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USE
To select a specific database and then perform operations using this command.
Syntax
USE database name;
For example
USE college;
CREATE TABLE
To create a new table in a database.
Syntax
CREATE TABLE table_name(
Column1 datatype,
Column2 datatype,
Column3 datatype,
……..
);
Example
CREATE TABLE student(
id INT,
name VARCHAR(30),
gpa DECIMAL(3,2)
);
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DESCRIBE
To describe the columns in the table.
For example
describe STUDENT;
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INSERT INTO
To insert new records in a table.
Syntax
INSERT INTO table_ name VALUES (value1,value2,…);
OR
INSERT INTO table_ name VALUES
(values1, values2, values3),
(values1, values2, values3), ----- inserts more than one row -----
(values1, values2, values3);
OR
INSERT INTO student (column 1 , column2,… ) VALUES (Values1, values2…); --- inserts specific columns ------
For example
INSERT INTO student VALUES
(100,'praba', 8.9),
(102,'vani', 9.8);
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ALTER
To delete, add or modify columns in an existing table.
Syntax:
ALTER TABLE table _ name
ADD column_ name datatype;
For example
ALTER TABLE student
ADD dept VARCHAR (30);
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SELECT
To select data from a database.
Syntax
SELECT column1,column2,….
FROM table_ name ;
OR
SELECT * FROM table_ name;
For example
SELECT * FROM student;
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SELECT name FROM student;
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WHERE
WHERE is a clause. It is used to filter records.
Syntax
SELECT column1, column2 , ….
FROM table_ name
WHERE condition;
For example
SELECT * FROM student
WHERE id=100;
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UPDATE
To modify the existing records in a table.
Syntax
UPDATE table_ name
SET column1=value1, column2=value2,….
WHERE condition;
For example
UPDATE student
SET gpa=9.00
WHERE id=100;
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DELETE
To delete existing records in a table.
Syntax
DELETE FROM table_ name
WHERE condition;
For example
DELETE FROM student
WHERE id=102;
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I hope this blog is most helpful to you.
Thank you.