- #1
late347
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I have a gut feeling that I will retake a test about these subjects.
Do you know good resources about creating ER diagram and relational model for database (sql database primarily)
Sometimes even creating a correct ER Diagram (chen notation) feels difficult and confusing. These type of homework problems have been things like word problems where we must construvt the ER diagram from a short written description.
For relational model... I think I can create relational model when I have the correctly defined ER diagram from which to begin work...
I think I could also use some resources for SQL queries but I do know already some basic queries. I studied some basic queries at w3school and I took the quiz about SQL but still I don't really have good enough understanding for a test at our school.
But I don't quite fully understand the logic begind the queries. Especially
Left join, right join, aliases, inner join,
And the logic begind the where operator in SQL queries is a little bit fuzzy to me. Especially if you somehow combine multiple tables in a query. How are you supposed to know which fields(?) Are equal to which fields in let's say two tables...?
Do you know good resources about creating ER diagram and relational model for database (sql database primarily)
Sometimes even creating a correct ER Diagram (chen notation) feels difficult and confusing. These type of homework problems have been things like word problems where we must construvt the ER diagram from a short written description.
For relational model... I think I can create relational model when I have the correctly defined ER diagram from which to begin work...
I think I could also use some resources for SQL queries but I do know already some basic queries. I studied some basic queries at w3school and I took the quiz about SQL but still I don't really have good enough understanding for a test at our school.
But I don't quite fully understand the logic begind the queries. Especially
Left join, right join, aliases, inner join,
And the logic begind the where operator in SQL queries is a little bit fuzzy to me. Especially if you somehow combine multiple tables in a query. How are you supposed to know which fields(?) Are equal to which fields in let's say two tables...?