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Language SQL SQL Adv Reference: W3School - http://www.w3schools.com/sql/default.asp http://www.tomjewett.com/dbdesign/dbdesign.php?page=recursive.

1 Language SQL SQL Adv Reference: W3School SQL Aliases SQL aliases are used to give a table, or a column in a table, a temporary name. Aliases are often used to make column names more readable. An alias only exists for the duration of the query. Alias Column Syntax SELECT column_name AS alias_name FROM table_name Alias Table Syntax SELECT column_name(s) FROM table_name AS alias_name; Or SELECT column_name(s) FROM table_name alias_name; 1

2 SQL HAVING Clause The HAVING clause was added to SQL because the WHERE keyword could not be used with aggregate functions. SELECT column_name(s) FROM table_name WHERE condition GROUP BY column_name(s) HAVING condition ORDER BY column_name(s); SQL HAVING Clause Write a SQL query to display the buildingid that the apartmentrentprice average is bigger than 800; SELECT apartmentbuildingid, AVG(apartmentRentPrice) AS priceavg FROM apartment GROUP BY apartmentbuildingid HAVING priceavg > 800; 2

3 Exercises 1. Write a query to display all buildings with the name of the city showing the fields buildingaddress, buildingzipcode and cityname. Using an Alias to change the name of the columns to Addresss, ZipCode and City; 2. Write a SQL query to display the name of the cities that has more than 3 apartments for rent; 3. Write a SQL query to display the list of building with all columns that the apartmentrentprice average is bigger than 1000; 4. Write a SQL query to display the name of the country that has 2 or more cities registered. 1. SELECT buildingaddress AS Address, buildingzipcode AS ZipCode, cityname AS City FROM building INNER JOIN city ON cityid=buildingcityid; 2.SELECT cityname, COUNT(cityId) as A1 FROM building INNER JOIN city ON (buildingcityid = cityid) INNER JOIN apartment ON (apartmentbuildingid = buildingid) GROUP BYcityName HAVING A1 > 3; 3

4 3. SELECT * FROM building WHERE buildingid IN (SELECT apartmentbuildingid FROM apartment GROUP BY apartmentbuildingid HAVING AVG(apartmentRentPrice) > 800); 4. SELECT countryname FROM country INNER JOIN city ON countryid= citycountryid GROUP BY countryid HAVING COUNT(countryId) >= 2; The SQL SELECT DISTINCT Statement The SELECT DISTINCT statement is used to return only distinct (different) values. Inside a table, a column often contains many duplicate values; and sometimes you only want to list the different (distinct) values. The SELECT DISTINCT statement is used to return only distinct (different) values. SELECT DISTINCT column1, column2,... FROM table_name; Ex.: SELECT DISTINCT countryname FROM Country; 4

5 SQL NULL Values NULL values represent missing unknown data. By default, a table column can hold NULL values. It is not possible to test for NULL values with comparison operators, such as =, <, or <>. We will have to use the IS NULL and IS NOT NULL operators instead. SQL Syntax SELECT LastName,FirstName,Address FROM Persons WHERE Address IS NULL Assign a value to a Null Field; SELECT IFNULL(apartmentRentPrice, 0) FROM apartments Exercises 1. Using Distinct, write a SQL query to Display a list of cities, avoiding to duplicate the cityname; 2. Write a SQL to display all cities that don t have a country assign; 3. Write a SQL to display all cities that have a country assign; 4. Write a SQL to display all apartments that don t have a rent price; 5. For the apartment that doesn t have a rent price, write a SQL query to display the value 0 instead of NULL; 6. Write a SQL query to display the rent price average at the table apartment; 7. Write a SQL query to display the rent price average at the table apartment, but now, specify the value 0 when the rent price is null, compare the results; 5

6 1. SELECT DISTINCT cityname FROM city; 2. SELECT * FROM city WHERE citycountryid IS NULL; 3. SELECT * FROM city WHERE citycountryid IS NOT NULL; 4. SELECT * FROM apartment WHERE apartmentrentprice IS NULL; 5. SELECT IFNULL(apartmentRentPrice, 0) FROM apartment; 6. SELECT AVG(apartmentRentPrice) FROM apartment; 7. SELECT AVG(IFNULL(apartmentRentPrice, 0)) FROM apartment; 6

7 SQL LIKE Wildcard SQL % A substitute for zero or more characters WHERE City LIKE '%tre%'; SQL _ A substitute for a single character WHERE City LIKE '_ontreal'; ORACLE SQL SERVER SQL [charlist] search all Cities starting with "b", "s", or "p" WHERE City LIKE ' [bsp]%'; SQL [charlist] search all Cities starting with "b", "s", or "p" WHERE City LIKE ' [bsp]%'; SQL [charlist] search all Cities starting with "a", "b", or "c" WHERE City LIKE ' [a-c]%'; SQL [charlist] search all Cities not starting with "b", "s", or "p" WHERE City LIKE ' [!bsp]%'; Or WHERE City NOT LIKE '[bsp]% Exercises 1. Write a SQL to display the building address where has the city name starting by M; 2. Write a SQL to display the building address where doesn t have the city name starting by M; 3. Write a SQL to display the building address where the third character of the city name is a N; 7

8 1. SELECT cityname, buildingaddress FROM building INNER JOIN city ON (buildingcityid = cityid) WHERE ( cityname LIKE "m%") 2. SELECT cityname, buildingaddress FROM building INNER JOIN city ON (buildingcityid = cityid) WHERE ( cityname NOT LIKE "m%") 3. SELECT cityname, buildingaddress FROM building INNER JOIN city ON (buildingcityid = cityid) WHERE (cityname LIKE " n%") MySQL DATE_FORMAT() Function The DATE_FORMAT() function formats a date as specified by a format mask. DATE_FORMAT(date, format_mask) Ex.: SELECT DATE_FORMAT(" ", "%Y"); 8

9 Format Description %a Abbreviated weekday name (Sun to Sat) %b Abbreviated month name (Jan to Dec) %c Numeric month name (0 to 12) %D Day of the month as a numeric value, followed by suffix (1st, 2 nd ) %d Day of the month as a numeric value (01 to 31) %e Day of the month as a numeric value (0 to 31) %f Microseconds ( to ) %H Hour (00 to 23) %h Hour (00 to 12) %I Hour (00 to 12) %i Minutes (00 to 59) %j Day of the year (001 to 366) %k Hour (0 to 23) %l Hour (1 to 12) Format Description %j Day of the year (001 to 366) %k Hour (0 to 23) %l Hour (1 to 12) %M Month name in full (January to December) %m Month name as a numeric value (00 to 12) %p AM or PM %r Time in 12 hour AM or PM format (hh:mm:ss AM/PM) %S Seconds (00 to 59) %T Time in 24 hour format (hh:mm:ss) %U Week where Sunday is the first day of the week (00 to 53) %u Week where Monday is the first day of the week (00 to 53) %W Weekday name in full (Sunday to Saturday) %Y Year as a numeric, 4-digit value %y Year as a numeric, 2-digit value MySQL CONCAT() Function The CONCAT() function concatenates two or more expressions together. CONCAT(expression1, expression2, expression3,...) Ex.: SELECT CONCAT("SQL ", "Tutorial ", "is ", "fun!") AS ConcatenatedString; 9

10 Exercises 1. Write a SQL query to display the contractid with the contractstartdate the date should appears in this format ex.: (10-Nov-2017) 2. Write a SQL query to display the contractid with the contractstartdate and the contractenddate, the date should appears only with the year ex.: 2017; 3. Write a SQL query to display the contractid with the number of year that the contract is valid; 4. Write a SQL query to display present date and time (server datetime) using the follow format Ex.10 November :30:05, using an alias datenow ; 5. Write a SQL query to display in one column the buildingaddress and the buildingzipcode using an alias Address; 6. Write a SQL query to display in one column the buildingaddress, buildingzipcode and cityname using an alias Address; The message should appears using the follow format: Address: 30, Rue Sheerbroke - ZipCode: Y6T City Name: Quebec 7. Write a SQL query to display present date and time (server datetime). The message should appears using the follow format Ex. Montreal November 1 st, :30:05, using an alias datenow. 1.SELECT contractid, DATE_FORMAT(contractStartDate, "%d-%b-%y") FROM contract; 2.SELECT contractid, DATE_FORMAT(contractStartDate, "%Y"), DATE_FORMAT(contractEndDate, "%Y") FROM contract; 3.SELECT contractid, (DATE_FORMAT(contractEndDate, "%Y")- DATE_FORMAT(contractStartDate, "%Y"))as numberyear FROM contract; 4. SELECT DATE_FORMAT(now(), "%d-%m-%y %H:%i:%S") as DateNow; 5. SELECT CONCAT(buildingAddress,' ',buildingzipcode) as Address FROM BUILDING; 6. SELECT CONCAT('Address: ',buildingaddress,' - ZipCode: ',buildingzipcode, ' - City Name: ',cityname) as Address FROM BUILDING INNER JOIN city ON (cityid = buildingcityid); 7. SELECT CONCAT('Montreal ', DATE_FORMAT(now(), "%M %D, %Y")) as DateNow; 10

11 MySQL REPLACE() Function The REPLACE() function replaces all occurrences of a specified string. REPLACE(string, from_substring, to_substring) Ex.: SELECT REPLACE("SQL Tutorial", "SQL", "HTML"); MySQL FORMAT() Function The FORMAT() function formats a number as a format of "#,###.##", rounding it to a certain number of decimal places. Then it returns the result as a string. FORMAT(number, decimal_places) SELECT FORMAT( , 2); 11

12 MySQL LTRIM() Function The LTRIM() function removes leading spaces from a string. LTRIM(string) Ex.: SELECT LTRIM(" SQL Tutorial") AS LeftTrimmedString; Exercises 1. Write a SQL query to display the cityname, and replace the city Montreal to MTR use an alias cityname. 2. Write a SQL query to display the tenatname, and replace the letter e on the name to the number 4, use an alias tenantname. 3. Write a SQL query to display the apartmentrentprice that is bigger or equal to 1000; the Result should appears respecting the follow format: $ 1, CAD use an alias rentprice. 12

13 1. SELECT REPLACE(cityName, "Montreal", "MTR") from city; 2. SELECT REPLACE(tenantName, "e", "4") from tenant; 3. SELECT CONCAT('$ ', FORMAT(apartmentRentPrice, 2), ' CAD') AS RentPrice FROM apartment WHERE apartmentrentprice >= 1000; PROCEDURES A procedure (often called a stored procedure) is a subroutine like a subprogram in a regular computing language, stored in database. A procedure has a name, a parameter list, and SQL statement. How to create a procedure DELIMITER $$ CREATE PROCEDURE displaytenant () BEGIN SELECT * FROM tenant; END$$ DELIMITER ; 13

14 PROCEDURES How to use a procedure CALL displaytenant(); How to delete a procedure DROP procedure IF EXISTS displaytenant; PROCEDURES WITH PARAMETERS DELIMITER $$ CREATE PROCEDURE displaytenant (IN id int, tname Varchar(45)) BEGIN SELECT * FROM tenant where tenantid=id and tenantname = tname; END$$ DELIMITER ; Using procedure CALL displaytenant(1, 'Tara Bradford'); 14

15 Exercises 1. Write a procedure to insert a new tenant (tenantname and tenantphone); 2. Using the procedure that you created before insert a new tenant (name: Mickey Mouse, Phone : ) 3. Delete the procedure that you create at que question Write again a procedure to insert a new tenant (tenantname and tenantphone) but now when you execute the procedure should appears the last insert data in your screen as a result, to confirm that worked; 5. Test your procedure inserting a new tenant (name: Minie Mouse, Phone : ) 1. DELIMITER $$ CREATE PROCEDURE inserttenant (IN tname VARCHAR(45), tphone Varchar(20)) BEGIN INSERT INTO tenant (tenantname, tenantphone) VALUES (tname, tphone); END$$ DELIMITER ; 2. CALL inserttenant('mickey Mouse', ' '); 3. DROP procedure IF EXISTS inserttenant; 4. DELIMITER $$ CREATE PROCEDURE inserttenant (IN tname VARCHAR(45), tphone Varchar(20)) BEGIN INSERT INTO tenant (tenantname, tenantphone) VALUES (tname, tphone); SELECT * from tenant order by tenantid DESC LIMIT 1; END$$ DELIMITER ; 5. CALL inserttenant('minie Mouse', ' '); 15

MySQL triggers The MySQL trigger is a database object that is associated with a table. It will be activated when a defined action is executed for the table.

16 MySQL triggers The MySQL trigger is a database object that is associated with a table. It will be activated when a defined action is executed for the table. The trigger can be executed when you run one of the following MySQL statements on the table: INSERT, UPDATE and DELETE and it can be invoked before or after the event. 16

Reference: W3School -

Language SQL SQL Adv Reference: W3School - http://www.w3schools.com/sql/default.asp http://www.tomjewett.com/dbdesign/dbdesign.php?page=recursive.php Recursive Associations/Relationship A recursive association