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Crud Operations in SQL

Answer»

CRUD is an abbreviation for Create, Read, Update and Delete. These 4 operations comprise the most basic database operations. The relevant commands for these 4 operations in SQL are:


  • Create: INSERT

  • Read: SELECT

  • Update: UPDATE

  • Delete: DELETE

The above image shows the pillars of SQL CRUD operations.


  • INSERT: To insert any new data ( create operation - C ) into a database, we use the INSERT INTO statement.

SQL Syntax:

INSERT INTO name_of_table(column1, column2, ....)
VALUES(value1, value2, ....)

Example:

INSERT INTO student(ID, name, phone, class)
VALUES(1, 'Scaler', '+1234-4527', 12)

For multiple rows,

SQL Syntax:

INSERT INTO name_of_table(column1, column2, ....)
VALUES(value1, value2, ....),
(new_value1, new_value2, ...),
(....), ... ;

Example:

INSERT INTO student(ID, name, phone, class)
VALUES(1, 'Scaler', '+1234-4527', 12),
(2, 'Interviewbit', '+4321-7654', 11);

The above example will insert into the student table having the values 1, Scaler, +1234-5678 and 12 to the columns ID, name, phone and class columns.


  • SELECT: We use the select statement to perform the Read ( R ) operation of CRUD.

SQL Syntax:

SELECT column1,column2,.. FROM name_of_table;

Example:

SELECT name,class FROM student;

The above example allows the user to read the data in the name and class columns from the student table.


  • UPDATE: Update is the ‘U’ component of CRUD. The Update command is used to update the contents of specific columns of specific rows.

SQL Syntax:

UPDATE name_of_table
SET column1=value1,column2=value2,...
WHERE conditions...;

Example:

UPDATE customers
SET phone = '+1234-9876'
WHEREID = 2;

The above SQL example code will update the table ‘customers’ whose ID is 2 with the new given phone number.

  • DELETE:

The Delete command is used to delete or remove some rows from a table. It is the ‘D’ component of CRUD.

SQL Syntax:

DELETE FROM name_of_table
WHERE condition1, condition2, ...;

Example:

DELETE FROM student
WHERE class = 11;

The above SQL example code will delete the row from table student, where the class = 11 conditions becomes true.


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