Bugl — code interview practice that feels like a game

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Flash cards

Review the key moves

1/4

Core idea

What is the main idea behind SQL DROP CONSTRAINT Keyword?

Lesson checks

Short Mimo-style checks built from this lesson's code, terms, and sequence.

1Quick choice

Which statement best captures the main point of this lesson?

2Fill blank

Complete the missing token from the example code.

___ TABLE Persons

3Order

Put the learning moves in the order that makes the concept easiest to apply.

DROP a FOREIGN KEY Constraint

DROP a PRIMARY KEY Constraint

DROP a UNIQUE Constraint

The DROP CONSTRAINT command is used to delete a UNIQUE, PRIMARY KEY, FOREIGN KEY, or CHECK constraint.

To drop a UNIQUE constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT UC_Person;

MySQL

ALTER TABLE Persons
DROP INDEX UC_Person;

To drop a PRIMARY KEY constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT PK_Person;

MySQL

ALTER TABLE Persons
DROP PRIMARY KEY;

To drop a FOREIGN KEY constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Orders
DROP CONSTRAINT FK_PersonOrder;

MySQL

ALTER TABLE Orders
DROP FOREIGN KEY FK_PersonOrder;

To drop a CHECK constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT CHK_PersonAge;

MySQL

ALTER TABLE Persons
DROP CHECK CHK_PersonAge;