SQL commonly used statements 1

Posted May 28, 20203 min read

(CREATE TABLE Order_T(OrderID NUMBER(5,0) NOT NULL, OrderDate DATE DEFAULT SYSDATE,CustomerID NUMBER(3,0), CONSTRAINT Order_PK PRIMARY KEY(OrderID));
(Default DATE format:DD-MON-YY HH:MI:SS AM/PM
(DROP TABLE Order_T; DROP TABLE Customer-T CASCADE CONSTRAINTS;
(INSERT INTO Order_T VALUES(12001, '10/16/2015', 99);
(DELETE FROM Customer_T WHERE CustomerID = 101;
(ALTER TABLE Customer_T MODIFY CustomerAddress VARCHAR2(30);
(ALTER TABLE Order_T
ADD CONSTRAINT Order_FK FOREIGN KEY(CustomerID) REFERENCES Customer_T(CustomerID);
(ALTER TABLE Customer_T ADD(CustomerCity VARCHAR2(20), CustomerState CHAR(2), CustomerPostalCode VARCHAR2(9));
(UPDATE Order_T SET OrderDate = '12/28/2015' WHERE OrderID = 12002;
(SELECT AVG(ProductStandardPrice) AS Average_Price FROM Product_T;

SELECT * FROM Product_T WHERE ProductDescription LIKE '%Desk%'; [(%):any collection of characters(_):exactly one character(e.g., '_-Drawer%') Note:it is case sensitive]
SELECT ProductDescription, ProductStandardPrice FROM Product_T WHERE ProductStandardPrice BETWEEN 200 AND 300;(both 200 and 300 are included)
SELECT * FROM Customer_T WHERE CustomerPostalCode IS NULL;
SELECT ProductDescription, ProductStandardPrice FROM Product_T WHERE ProductDescription LIKE '%Desk' OR ProductDescription LIKE '%Table' AND ProductStandardPrice > 300; [Condition AND, only works on like %Table , not on %Desk , NOT(AND(OR]
SELECT CustomerName,CustomerCity,CustomerState FROM Customer_T WHERE CustomerState IN('FL','TX','CA') ORDER BY CustomerState,CustomerName;
SELECT ProductID, ProductDescription, ProductStandardPrice FROM Product_T WHERE ProductStandardPrice =(SELECT MAX(ProductStandardPrice) FROM Product_T WHERE ProductFinish='Natural Ash') AND ProductFinish='Natural Ash';
SELECT ProductFinish, COUNT(ProductID) AS Total FROM Product_T GROUP BY ProductFinish;
SELECT ProductLineID, MIN(ProductStandardPrice) AS Min_Price, MAX(ProductStandardPrice) AS Max_Price FROM Product_T GROUP BY ProductLineID;
SELECT CustomerState,COUNT(CustomerID) FROM Customer_T GROUP BY CustomerState HAVING COUNT(CustomerID) > 1;[HAVING only used with a GROUP BY clause]
SELECT CustomerState AS State, COUNT(CustomerID) AS Total_Customers FROM Customer_T GROUP BY CustomerState HAVING COUNT(CustomerID) > 1 ORDER BY Total_Customers DESC; [CANNOT use Total_Customers in HAVING ]
SELECT ProductFinish, ROUND(AVG(ProductStandardPrice), 2) AS Avg_Price FROM Product_T WHERE ProductFinish IN('Cherry','Natural Ash','Natural Maple','White Ash') GROUP BY ProductFinish;
SELECT * FROM Student, Department WHERE Student.dno = Department.dno; [Equi-Join, Common columns appear(redundantly) in the result table.]
SELECT * FROM Student INNER JOIN Department ON Student.dno = Department.dno; [inner join]
SELECT * FROM Student INNER JOIN Department USING dno; [inner join, Require identical column names for the PK and FKs of dno, Only MATCHED rows are selecteded, Establish an equi-join in the FROM clause]
SELECT * FROM Student NATURAL JOIN Department ON aStudent.dno = Department.dno; [Natural join, Same as an equi-join except that one of the duplicate columns is eliminated in the result table]
SELECT * FROM Student LEFT OUTER JOIN Department ON Student.dno = Department.dno; [Left Outer Join, Return all rows of the left-hand-side table no matter whether there is a match or not, and leave non matched column with null value]
SELECT * FROM Customer_T o LEFT JOIN Order_T c ON c.Customerid = o.Customerid [List all customers associated with their order info, including customers with no order info.]
SELECT FLOOR(year/10)10 AS decade, Round(COUNT()/Total_100,1) AS Action_Distribution FROM movies,(select count() as Total from movies where genre = 'Action') WHERE genre = 'Action' GROUP BY FLOOR(year/10)*10 ORDER BY decade; [Calculate the distribution of Action movies(genre = 'Action') in different decades]
SELECT decade1 as decade, Round(Action_Movies/All_Movies_100,1) AS Action_Proportion from(SELECT FLOOR(year/10)_10 AS decade1, COUNT(
) AS Action_Movies FROM movies WHERE genre = 'Action' GROUP BY FLOOR(year/10)10),(SELECT FLOOR(year/10)_10 AS decade2, COUNT() AS All_Movies FROM movies GROUP BY FLOOR(year/10)*10) where decade1 = decade2; [Find the proportion of Action movies in different decades]