![]() The table can contain only one primary keyĪ primary key cannot be a NULL value in the databases, but in the case of SQLite, it can be assigned a NULL value, because of the “long-standing coding oversight”.Ī table should have only one primary key, but multiple columns can be defined in a single primary key, when multiple columns are being used as a single primary key, then it is called a composite primary key.The primary key should be referred to as the particular foreign key of another table.This means that one can, for example, insert a string into a column. The data inserted in the rows of the column of the Primary key should be unique SQLite is a database engine written in the C programming language.The column of the primary key cannot be defined with the NULL value.Primary keys are very essential when creating a database that has a variety of tables, and to create relationships among the different databases, the primary key is used. These two properties are the foreign key from ApplicationUser Table. ![]() ![]() The table can be created without using the primary key, but if the table is using the primary key, then only one primary key can be assigned to the table. In this ShareDocument table I have two property which are SenderUserId and ReceiverUserId. ![]() There are many constraints, some of them are:Ī primary key is the unique column of the table, which ensures the entries inserted in the column should be unique and is also used to refer to the foreign key of other tables. What are the constraints in SQLiteĬonstraints are the principles, according to which data of the same data type is inserted into the table, it organizes the structure of the column and also ensures the reliability of the data which is stored in the table. #Sqlitestudio foreign key to same table how to#So what are constraints and how do they work in SQLite? This write-up is a comprehensive guide about constraints and on how to use the PRIMARY key constraint in SQLite. SQLite is a database management system, which is used to manage the data of the relational database just like MySQL, it also contains a lot of constraints such as UNIQUE, PRIMARY KEY, and FOREIGN KEY like other databases. ![]()
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