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Sql updating tables with foreign keys

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If all validation succeeds, then the transaction commits.

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Unlike on-disk tables, there is no locking and write-write conflicts are detected (error 41302) if concurrent transactions update the same rows.The table containing the foreign key is called the child table, and the table containing the candidate key is called the referenced or parent table.Primary keys serve as unique identifiers for the records in a table, while foreign keys are used to link related tables together.When you drop a table, any constraints that were defined in the statement used to create that table are also dropped.If you re-create a table that was dropped, it must have a definition that conforms to the foreign key constraints referencing it.The FOREIGN KEY constraint also prevents invalid data from being inserted into the foreign key column, because it has to be one of the values contained in the table it points to.