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How do you select all the records from a table named Persons where the value of the column FirstName starts with an a?
To select all records from the "Persons" table where the value of the column "FirstName" starts with 'a', you can use the following SQL query: SELECT * FROM Persons WHERE FirstName LIKE 'a%'; This query will retrieve all records where the "FirstName" column starts with the letter 'a'.
With SQL how can you delete the records where the FirstName is Peter in the Persons Table?
To delete records where FirstName is Peter in the Persons Table, you can use the following SQL query: DELETE FROM Persons WHERE FirstName = 'Peter';
What is the difference between primary key and secondary key in database?
The primary key is the field containing unique values that aid in database operations. The secondary key is used in addition or as an alternate to the primary key. Both are candidate keys, it's just that one was chosen to be primary.
What are the differences between super key primary key candidate key and foreign key?
Super key: A set of attributes that uniquely identifies a tuple in a table. Primary key: A specific super key chosen to uniquely identify each tuple in a table and must be unique and not null. Candidate key: Any super key that could be chosen as the primary key. Foreign key: A field in a table that is a primary key in another table, used to establish a relationship between the two tables.
What is the difference between a Primary Key and a Secondary Key?
A Primary Key is a unique identifier for each record in a database table and is used to enforce entity integrity. A Secondary Key is a non-unique index that is used for querying and organizing data efficiently but does not have the constraint of uniqueness.
How do you select a column named FirstName from a table named Persons?
In order to select a column named FirstName from a table named Persons, you should run the following MySQL query:SELECT FirstName FROM Persons
How is a primary key specified?
You select the column were the entity you want to make a primary key is located and then u right click the column and then select set as primary key.
How do you select all the records from a table named Persons where the value of the column FirstName starts with an a?
To select all records from the "Persons" table where the value of the column "FirstName" starts with 'a', you can use the following SQL query: SELECT * FROM Persons WHERE FirstName LIKE 'a%'; This query will retrieve all records where the "FirstName" column starts with the letter 'a'.
How can a Foreign Key and a Primary Key interact with each other?
In some database systems, A Foreign Key that is set on one column (the child column ) has to point to another column (the parent column ) that is indexed. The parent column could be a primary key, since a primary key creates an index. Primary keys also keep values in the parent column unique, which can ensure unique records in the parent column's table; having a unique key on the child column can further enforce unique data that links with the unique records in the parent column .
How do you select all the records from a table named Persons where the value of the column FirstName is Peter?
SELECT * FROM Persons WHERE FirstName='Peter'
Is it possible for the computer to generate values that are used as the primary key column?
Yes. Often times, an automatically generated key column will be a normal primary key using the auto_increment attribute.
Why you need primary key and foreign key?
In sql you use primary key more than one column in a table
What is primery key?
primary key is a column or set of columns (called composite primary key ) that identify the table & make every table unique .value of a primary key can not duplicated & can not be NULL .
What is primary key constraint?
Primary Key is a Constraint Used to avoid Duplicate entries in database table and you define primary key the column doesn't allow NULL values.
What are the differences between primary key foreign key and candidate key?
A primary key is a column which uniquely identifies the records in a table. In a broad sense, a primary key is the mixture of a unique key and an index: A column with a primary key is indexed to deliver a faster query, and doesn't allow duplicate values to ensure specific data. Most programmers recommend all tables having a primary key (and only one) to enhance the speed of queries and overall database performance. An example of a primary key may be found in a table named "departments," which might have a column named "department_number" that uniquely identifies each department in the table with a number.A foreign key is a column (the child column ) in a table which has a corresponding relationship and a dependency on another column (the parent column ) that is usually in a different table. Parent columns can have multiple child columns, but a child column can only have one parent column. The child column is the column with the foreign key; the parent column does not have the foreign key "set" on it, but most databases require the parent column to be indexed. Foreign keys are made to link data across multiple tables. A child column cannot have a record that its parent column does not have. Say a table named "employees" has 20 employees (rows) in it. There are 4 departments in the "departments" table. All 20 employees must belong to a department, so a column in the "employees" table named "department" would point to the primary key in the "departments" table using a foreign key. Now all employees must belong to a department as specified by the "departments" table. If a department isn't specified in the "departments" table, the employee cannot be assigned to it.A candidate key would be any key which could be used as the primary key, which means that the combination of the columns, or just the single column would create a unique key. You would then need to determine which of these candidate keys would work best as your primary key.
How do you create a primay key in Oracle?
You can create a primary key column in an oracle table using the PRIMARY KEY keyword. Assuming you have an employee table that has employee information and has a column called emp_num. you can create a primary key in the table using the below command. ALTER TABLE tbl_employee_info add CONSTRAINT emp_pk PRIMARY KEY (emp_num) If you execute the above command in your database, emp_num will become the primary key of the table tbl_employee_info.
What is key constraints?
Primary Key is a Constraint Used to avoid Duplicate entries in database table and you define primary key the column doesn't allow NULL values.
