What does constraints mean in SQL?

A constraint in SQL is an inter-table relationship that keeps the data in the table consistent. These constraints work to prevent users from entering invalid data. They can be either mandatory or non-mandatory. For example, a unique constraint is a mandatory constraint. It ensures that there can be no duplicate entries of the same data in the column. Another example of a mandatory constraint is a foreign key constraint. It ensures that the values of the primary key (the column with the unique identifier) are linked

What is the difference between a constraint and a filter in SQL?

A filter in SQL is used to restrict the data that is returned based on a condition. A constraint can be used to limit the values that can be stored in a column or a table. Examples of constraints include primary key, foreign key, check constraints, and other business rules.

What is constraint clause in SQL?

A constraint clause in SQL is the part of a SQL query that constrains the result set. It tells the database what type of data can be returned, based on the contents of the column. For example: if you have a table called Payments that contains information about credit card payments, you might want to add a constraint that limits the results to include only payments made by credit card. You would use the PaymentId column in the WHERE clause to constrain the results to only show payments made by

What is a constraint name in SQL?

A constraint name is a name given to a single column or a group of columns to help you identify it. It is most often used to specify the name of a primary key or a foreign key. If you want to refer to a primary key constraint, you can call it PK. If you want to refer to a foreign key constraint, you can call it FK. You can also refer to a primary key constraint using the name of the table that it is linked to.

What does the constraint mean in SQL?

A constraint is a rule that defines the allowable values for one or more columns. There are different types of constraints, and they do different things. For example, a check constraint enforces a condition that a column can only contain values that meet a specific condition. An index constraint defines the order that data is stored in an index. A foreign key constraint enforces referential integrity by linking one table to another. There are also other types of constraints.