ITM 500 Lecture 3: Week 3 Notes

• School: Ryerson University
• Department: Information Technology Management
• Course: ITM 500
• Professor: Raymond Moss

Document Summary

Sql queries: crsdesc coursedescription, like not like, like just means equal" and not like means not equal". What does the 1. 1 represent its an expression to show that the salary has increased. Aggregate queries (component of sql queries): count a function that takes a parameter, because we are counting rows, there is not column reference, so we use the whole column values. Count (distinct) means that only the number of unique values (the different value occurrences) for that column will be counted. If student 222 has enrolled 6 times there will be 6 entries in the enrollment table where the value 222 is present but because of the keyword distinct it will only be counted. Is not null is null: not null count rows, count distinct values. Sql allows you to use the percent sign ( % ) and underscore ( _ ) wildcard characters to make matches when the entire string is not known: