SQL Queries

SQL Queries

(1) The SQL CREATE TABLE Statement:

Syntax

CREATE TABLE table_name (column1 datatype,column2 datatype,column3 datatype,....);

Example

CREATE TABLE Persons (PersonID int, LastName varchar(255),FirstName varchar(255),Address varchar(255), City varchar(255));

(2) SQL INSERT INTO Statement

INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1,value2, value3, ...);

Example

INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode,Country)VALUES ('Cardinal', 'Tom B. Erichsen', 'Skagen 21', 'Stavanger', '4006', 'Norway');

(3) SQL SELECT Statement

(a) SELECT column1, column2, ... FROM table_name;        (b) SELECT * FROM table_name;

Example

(a) SELECT CustomerName, City FROM Customers;          (b) SELECT * FROM Customers;

(4) SQL SELECT DISTINCT Statement

SELECT DISTINCT column1, column2, ... FROM table_name;

Example

SELECT Country FROM Customers;

(5) The SQL WHERE Clause

SELECT column1, column2, ... FROM table_name WHERE condition;

Example

SELECT * FROM Customers WHERE Country='Mexico';

(6) The SQL ORDER BY Keyword

SELECT column1, column2, ... FROM table_name ORDER BY column1, column2, ...ASC|DESC;

Example

SELECT * FROM Customers ORDER BY Country;

(7) SQL UPDATE Statement

UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition;

Example

UPDATE Customers SET ContactName = 'Alfred Schmidt', City= 'Frankfurt' WHERE CustomerID = 1;

(8) SQL DELETE Statement

DELETE FROM table_name WHERE condition;

Example

DELETE FROM Customers WHERE CustomerName='Alfreds Futterkiste';

(9) SQL MIN() and MAX() Functions

MIN() Syntax

SELECT MIN(column_name) FROM table_name WHERE condition;

MAX() Syntax

SELECT MAX(column_name) FROM table_name WHERE condition;

Example

SELECT MIN(Price) AS SmallestPrice FROM Products;

SELECT MAX(Price) AS LargestPrice FROM Products;

(10) SQL COUNT(), AVG() and SUM() Functions

COUNT() Syntax

SELECT COUNT(column_name) FROM table_name WHERE condition;

AVG() Syntax

SELECT AVG(column_name) FROM table_name WHERE condition;

SUM() Syntax

SELECT SUM(column_name) FROM table_name WHERE condition;

Example

SELECT COUNT(ProductID) FROM Products;

SELECT AVG(Price) FROM Products;

SELECT SUM(Quantity) FROM OrderDetails;

(11) SQL LIKE Operator

SELECT column1, column2, ... FROM table_name WHERE columnN LIKE pattern;

Example

SELECT * FROM Customers WHERE CustomerName LIKE 'a%';

(12) SQL UNION Operator

SELECT column_name(s) FROM table1

UNION

SELECT column_name(s) FROM table2;

Example

SELECT City FROM Customers UNION SELECT City FROM Suppliers ORDER BY City;

(13) SQL GROUP BY Statement

SELECT column_name(s) FROM table_name WHERE condition GROUP BY column_name(s) ORDER BY column_name(s);

Example

SELECT COUNT(CustomerID), Country FROM Customers GROUP BY Country;

(14) SQL HAVING Clause

SELECT column_name(s) FROM table_name WHERE condition GROUP BY column_name(s) HAVING condition ORDER BY column_name(s);

Example

SELECT COUNT(CustomerID), Country FROM Customers GROUP BY Country HAVING COUNT(CustomerID) > 5;

(15) SQL DROP TABLE Statement

DROP TABLE table_name;

Example

DROP TABLE Shippers;

(16) SQL ALTER TABLE Statement

(a) ALTER TABLE table_name ADD column_name datatype;

(b) ALTER TABLE table_name MODIFY COLUMN column_name datatype;

Example

ALTER TABLE Persons ADD DateOfBirth date;

(17) SQL NOT NULL Constraint

Example

CREATE TABLE Persons ( ID int NOT NULL, LastName varchar(255) NOT NULL,

FirstName varchar(255) NOT NULL, Age int );

(18) SQL UNIQUE Constraint

Example

CREATE TABLE Persons (ID int NOT NULL, LastName varchar(255) NOT NULL,

FirstName varchar(255), Age int, UNIQUE (ID));

(19) SQL PRIMARY KEY Constraint

Example

CREATE TABLE Persons (ID int NOT NULL, LastName varchar(255) NOT NULL,

FirstName varchar(255), Age int, PRIMARY KEY (ID));

(20) SQL FOREIGN KEY Constraint

Example

CREATE TABLE Orders (OrderID int NOT NULL, OrderNumber int NOT NULL,

PersonID int, PRIMARY KEY (OrderID), FOREIGN KEY (PersonID) REFERENCES

Persons(PersonID));

(21) SQL Working With Dates

Example

SELECT * FROM Orders WHERE OrderDate='2008-11-11'

 

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