SQL FOREIGN KEY Constraint - W3Schools
The FOREIGN KEY constraint is used to prevent actions that would destroy links between tables. A FOREIGN KEY is a field (or collection of fields) in one table, that refers to the PRIMARY KEY in …
SQL FOREIGN KEY - W3Schools
The FOREIGN KEY constraint is a key used to link two tables together. A FOREIGN KEY is a field (or collection of fields) in one table that refers to the PRIMARY KEY in another table.
MySQL FOREIGN KEY Constraint - W3Schools
The FOREIGN KEY constraint is used to prevent actions that would destroy links between tables. A FOREIGN KEY is a field (or collection of fields) in one table, that refers to the PRIMARY KEY in …
MySQL Constraints - W3Schools
If there is any violation between the constraint and the data action, the action is aborted. Constraints can be column level or table level. Column level constraints apply to a column, and table level constraints …
W3Schools SQL Exercise
Exercise: SQL Foreign Key The FOREIGN KEY constraint is used to: Perform a comparison between a single column value and a range of other values Prevent actions that would destroy links between …
MySQL UNIQUE Constraint - W3Schools
The UNIQUE constraint ensures that all values in a column are different. Both the UNIQUE and PRIMARY KEY constraints provide a guarantee for uniqueness for a column or set of columns.
SQL DROP - W3Schools
DROP a FOREIGN KEY Constraint To drop a FOREIGN KEY constraint, use the following SQL: SQL Server / Oracle / MS Access:
SQL Keywords Reference - W3Schools
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W3Schools Exercise
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SQL DELETE Statement - W3Schools
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