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onstraints are critical components in databases. They restrict (constrain) what you can add, modify, or delete from tables with INSERT, UPDATE, and DELETE statements. Constraints let you restrict what can be placed in columns, rows, tables, or relationships between tables. That’s a tremendously broad statement that requires some qualification. So what are these restrictions and why are they important? |
As with the prior chapter, this chapter develops what and why before delving into the SQL implementation of database constraints that work with ...
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