SQL PRIMARY KEY Constraint - W3Schools
SQL PRIMARY KEY Constraint The PRIMARY KEY constraint is used to uniquely identify each record in a table. Primary keys must contain unique values, and cannot contain NULL values. …
MySQL PRIMARY KEY Constraint - W3Schools
MySQL PRIMARY KEY Constraint The PRIMARY KEY constraint uniquely identifies each record in a table. Primary keys must contain UNIQUE values, and cannot contain NULL values. A …
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 …
Python MySQL Create Table - W3Schools
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MySQL UNIQUE Constraint - W3Schools
Both the UNIQUE and PRIMARY KEY constraints provide a guarantee for uniqueness for a column or set of columns. A PRIMARY KEY constraint automatically has a UNIQUE constraint.
PHP MySQL Create Table - W3Schools
The column with PRIMARY KEY setting is often an ID number, and is often used with AUTO_INCREMENT Each table should have a primary key column (in this case: the "id" …
PostgreSQL Create Table - W3Schools
To create a new database table using the SQL Shell, make sure you are connected to the database. If not, follow the steps in the Get Started chapter of this tutorial.
MySQL CREATE TABLE Statement - W3Schools
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SQL ALTER TABLE Statement - W3Schools
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SQL INSERT INTO Statement - W3Schools
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