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Databases Querying Relational Databases Joining Table Data with SQL Inner Joins

Posted by orange sky
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orange sky
Front End Web Development Techdegree Student 4,945 Points

Inner join

Hello,

When you join 2 tables like the below, after ON do you always have to the name of a table dot the primary key equal to the name of the other table dot foreign key?

SELECT * FROM make INNER JOIN Model ON make.MakeID = Model.MakeID ;

2 Answers

chestopher collins
chestopher collins
1,086 Points

The only time I think its acceptable but NOT "Good Practice" is if the column name was unique, other wise putting the dot after the table specifies which column you want to join.

Alexander Nikiforov
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Alexander Nikiforov
Java Web Development Techdegree Graduate 22,175 Points
Alexander Nikiforov
.a{fill-rule:evenodd;}techdegree seal-36
Alexander Nikiforov
Java Web Development Techdegree Graduate 22,175 Points

I don't quite understand the question ...

Yes I think you always have to write condition on which you join tables.

How do you think SQL can infer which columns are equal ?

SQL cannot just know which columns to compare ...