A primary key must be
1. unique and cannot be null
2. unique and can be null
3. duplicated and cannot be null
4. duplicated and can be null
A primary key must be unique and cannot be null |
A primary key is a field used to identify records uniquely in a database. |
A primary key must always have a value and cannot be left blank. |
Option 1 is correct |
A primary key must be 1. unique and cannot be null 2. unique and can be...
1. Key resources of sugarbear hair company ( what unique steategic assets must the business have to complete.) 2. key activities of sugarbear hair company ( what can the company not do so it can focus on its key activities?) 3. Cost structure of sugarbear hair company. ( what are the business major cost drivers? how are they linked to revenue.)
Which of the following describes referential integrity? A. A Primary Key of a relational table must not contain a null value B. One fact must not be in multiple places C. The value for a foreign key attribute must either be null or match the one of the data value of that attribute in the table in which the attribute is a primary key D. Referential Integrity is a principle that prevents the use of redundancy, avoids null values and...
A database imposes several requirements on the structure of tables. Which of the following is not one of those requirements? A foreign key must be unique. A primary key must be unique. A primary key cannot be null (blank). A foreign key must be a primary key from another table.
Database Design and Management: The percent sign (%) and asterisk (*) symbols can be used with the LIKE comparison operator to create a search pattern. True or False? When translating an arc relationship to a physical design, you must turn the arc relationships into foreign keys. Assuming you are implementing an Exclusive Design, you must also create two Unique Key Constraints to ensure the Arc is implemented correctly. True or False? The explanation below is a User Defined integrity rule...
key attribute depends upon the whole primary key. 8. The result of normalization is that every A) Candidates B) Unique C) Primary D) Non-primary key attribute depends upon the whole primary key. 9. The result of normalization is that every A) Candidate B) Unique C) Primary D) Non-primary to show the 10. Increasingly, developers are using tools that can quickly create screen mockups, referred to as placement of information elements on a screen and the space needed for each element....
QUESTION 6 Which of the following statements best illustrates the "Key" constraint? The schema MUST be created before tables are added A primary key MUST NOT have duplicate values A foreign key value MUST have a value already present as a primary key in another table (or be NULL) A primary key value MUST have a value QUESTION 7 Which of the following statements best illustrates the "Referential Integrity" constraint? The schema MUST be created before tables are added A...
A foreign key value must exist in the table where it is a primary key. True? False?
True or False questions: 1. A data type mismatch error would occur when the primary key data data type is auto number and the foreign key in the related table is number. 2. The data type long integer is the same as integer. 3. When using SQL, the SELECT clause isolates tables in the database. 4. A Referential Integrity violation occur when the primary key is null. 5. When an REA model has 7 entities ,2 linking tables, 3 Resource...
The database(or the tables) are follow: CREATE TABLE employees ( id SERIAL NOT NULL PRIMARY KEY, name TEXT NOT NULL, salary REAL NOT NULL DEFAULT 25000.0 ); CREATE TABLE employee_audit_log ( employee_id INTEGER NOT NULL, occurred_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ); INSERT INTO employees(name, salary) VALUES ('Arnold Schwarznegger', 35000), ('Yuri Gargarin', 27000), ('Anakin Skywalker', 450000), ('Said Faroghi', 15000), ('Zino Holwerda', 8500); 1. Create a trigger for the employees table so that a new row is inserted in employee audit_log...
1- Explain, as best you can, why the primary key of the "one" side becomes the foreign key on the "many" side in a 1:M relationship?