DELETE statement is used to delete the records of a table.
DELETE FROM table_name WHERE condition;
If you want to delete a specific customer details from customer table:
DELETE FROM Customers WHERE CustomerName='john';
If you want to delete all the records of customer table:
DELETE FROM Customers;
UPDATE statement is used to edit the records of a table.
UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;
UPDATE Customers
SET CustomerName = 'john', City= 'Austria'
WHERE CustomerID = 6;
Whenever we use UPDATE Statement without WHERE clause it will Update all the records in the table.
UPDATE table_name
SET column1 = value1, column2 = value2...;
UPDATE Customers
SET CustomerName='john';
INSERT INTO statement is used to insert the records in table. We can insert records in table in two ways, the most commonly used way for insert is to specify both the column names and values.
In this method there is no need to specify the column names in SQL query, however make sure the order of the values and columns.
INSERT INTO table_name
VALUES (value1, value2, value3, ...);
INSERT INTO Customers
VALUES ('john', 'Michel john ', 'St 55', 'louse angelus', '4900', 'USA');
INSERT INTO table_name (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...);
INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country)
VALUES ('john', 'Michel john ', 'St 55', 'louse angelus', '4900', 'USA');
SQL is a standard language for sorting, manipulating and retrieving data from databases. SQL stands for Structured Query Language that let you access and manipulate databases.
Power of SQL:
Below are some most important and basic commands of SQL.
| Command | Description |
|---|---|
| SELECT | It extracts data from a database |
| UPDATE | It updates data in a database |
| DELETE | It deletes data from a database |
| INSERT INTO | It inserts new data into a database |
| CREATE DATABASE | It creates a new database |
| ALTER DATABASE | It modifies a database |
| CREATE TABLE | It creates a new table |
| ALTER TABLE | It modifies a table |
| DROP TABLE | It deletes a table |
| CREATE INDEX | It creates an index |
| DROP INDEX | It deletes an index |