2) Syntax of SQL [UPDATE, DELETE FROM, INSERT INTO]

Summary of Important SQL commands

SELECT	extracts data from a DB
UPDATE	updates data in a DB
DELETE	deletes data from a DB
INSERT INTO	inserts new data into a DB
CREATE DATABASE	creates a new DB
ALTER DATABASE	modifies a DB
CREATE TABLE	creates a new table
ALTER TABLE	modifies a table
DROP TABLE	deletes a table
CREATE INDEX	creates an index (search key)
DROP INDEX	deletes an index

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UPDATE

used to change the existing records in a table

UPDATE table_name
SET col1 = val1, col2 = val2, ...
WHERE condition # The WHERE clause specifies which record(s) that should be updated.
		# If you omit the WHERE clause, all records in the table will be updated.

Example

# Move the 2012 games from Londong to Paris
UPDATE games SET city='Paris'
WHERE yr = 2012

 

 

DELETE FROM

used to delete existing records in a table

 

DELETE FROM table_name
WHERE condition

 

Deleting ALL records:

DELETE FROM table_name

 

INSERT INTO

used to insert new records in a table

 

1. Specifying both the columns and the values to be inserted:

INSERT INTO table_name (col1, col2, col3, ...)
VALUES (val1, val2, val3, ...)

 

2. Specifying only the values (Adding values for all the columns of the table, and so the order of the values should be in the same order as the columns in the table):

INSERT INTO table_name
VALUES (val1, val2, val3, ...)