SQL Reminder Jiankang Yuan Martin Lemke

SQL Reminder - SELECT SELECT column_name1, column_name2, … FROM table_name SELECT * FROM table_name

SQL Reminder - SELECT IDNameProjectSemester 1PeterGeda5 2PaulEco System9 3MaryGeda7 Table ‚Software_Project‘ Query SELECT Name, Semester FROM Software_Project NameSemester Peter5 Paul9 Mary7 Result: Example

SQL Reminder - WHERE SELECT column_name1, column_name2, … FROM table_name WHERE column_nameX operator value Query SELECT Name, Semester FROM Software_Project WHERE Semester > 5 Result: NameSemester Paul9 Mary7 Example

SQL Reminder – Aggregate Functions AVG() - Returns the average value COUNT() - Returns the number of rows FIRST() - Returns the first value LAST() - Returns the last value MAX() - Returns the largest value MIN() - Returns the smallest value SUM() - Returns the sum etc.

SQL Reminder – GROUP BY SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name Example Query SELECT Project, COUNT(Name) FROM Software_Project WHERE Semester > 4 GROUP BY Project Result: ProjectCOUNT(Name) Geda2 Eco System1 Example Query SELECT Project, COUNT(Name) FROM Software_Project WHERE Semester > 4 GROUP BY Project Example Query SELECT Project, COUNT(Name) FROM Software_Project WHERE Semester > 4 GROUP BY Project Example Query SELECT Project, COUNT(Name) FROM Software_Project WHERE Semester > 4 GROUP BY Project Example Query SELECT Project, COUNT(Name) FROM Software_Project WHERE Semester > 4 GROUP BY Project

SQL Reminder - HAVING SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name HAVING aggregate_function(column_name) operator value Example Query SELECT Project, COUNT(Name) FROM Software_Project WHERE Semester > 4 GROUP BY Project HAVING COUNT(Name) > 1 Result: ProjectCOUNT(Name) Geda2

SQL Reminder – AND, OR, ORDER BY AND & OR Use AND and OR to join more conditions in the WHERE or HAVING clause ORDER BY SELECT column_name(s) FROM table_name ORDER BY column_name(s) ASC|DESC

SQL Reminder – CREATE TABLE CREATE TABLE table_name ( column_name1 data_type, column_name2 data_type, column_name3 data_type,.... ) Example CREATE TABLE seminar ( ID int, Name varchar(255), Topic varchar(255) ) Result IDNameTopic

SQL Reminder – INSERT INTO INSERT INTO table_name VALUES (value1, value2, value3,...) INSERT INTO table_name (column1, column2, column3,...) VALUES (value1, value2, value3,...) Example Query INSERT INTO Software_Project VALUES (4, John, News Analysis, 5) Result: IDNameProjectSemester 1PeterGeda5 2PaulEco System9 3MaryGeda7 4JohnNews Analysis5

SQL Reminder - UPDATE UPDATE table_name SET column1=value, column2=value2,... WHERE some_column=some_value Example Query UPDATE Software_Project SET Semester = 17 WHERE Name = ‚John‘ Result: IDNameProjectSemester 1PeterGeda5 2PaulEco System9 3MaryGeda7 4JohnNews Analysis17

SQL Reminder - DELETE DELETE FROM table_name WHERE some_column=some_value Example Query DELETE FROM Software_Project WHERE Project = ‚News Analysis‘ Result: IDNameProjectSemester 1PeterGeda5 2PaulEco System9 3MaryGeda7