Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
If a table contains duplicate rows, will a query display duplicate values by default? How can you eliminate duplicate rows from a query result?
Yes, they will be displayed by default. To eliminate duplicate records, you use the DISTINCT keyword after the word SELECT.
Yes, they will be displayed by default. To eliminate duplicate records, you use the DISTINCT keyword after the word SELECT.
See lessWhat is a synonym?
A synonym is a database object that allows you to create a kind of “link” or “alias” to another database object. This is often done to hide the name of the actual object for security reasons or to improve the maintenance of the code in the future.
A synonym is a database object that allows you to create a kind of “link” or “alias” to another database object. This is often done to hide the name of the actual object for security reasons or to improve the maintenance of the code in the future.
See lessWhat is a unique constraint? How is it different from a primary key?
A unique constraint is a constraint on a table that says that a column or set of columns needs to have unique values. It’s different from a primary key in that a table can only have one primary key, but a table can have zero, one, or many unique constraints. Unique constraints can also allow NULL vaRead more
A unique constraint is a constraint on a table that says that a column or set of columns needs to have unique values.
It’s different from a primary key in that a table can only have one primary key, but a table can have zero, one, or many unique constraints.
Unique constraints can also allow NULL values, but primary keys cannot.
See lessWhat is a surrogate key?
A surrogate key is a field in a table that has been created solely for the purpose of being the primary key. It has no other purpose than internal storage and reference number. For example, a customer may have an account number that is unique to them, but a customer_id field might be created on theRead more
A surrogate key is a field in a table that has been created solely for the purpose of being the primary key. It has no other purpose than internal storage and reference number.
For example, a customer may have an account number that is unique to them, but a customer_id field might be created on the table and used as the primary key, in case business rules change and mean that the account number is no longer unique.
See lessWhat is a composite key?
A composite key is a primary key that is made up of two or more fields. Often, primary keys are single fields, but in some cases, a row is identified by multiple fields. This is what a composite key is.
A composite key is a primary key that is made up of two or more fields. Often, primary keys are single fields, but in some cases, a row is identified by multiple fields. This is what a composite key is.
See lessWhat is a foreign key?
A foreign key is a field in a table that refers to a primary key in another table. It is used to link the record in the first table to the record in the second table.
A foreign key is a field in a table that refers to a primary key in another table. It is used to link the record in the first table to the record in the second table.
See lessWhat is a primary key?
A primary key is a column or set of columns that uniquely identifies a row in a table. It’s created on a table and ensures that the values in that column or columns must be unique and not NULL. This is often done using some kind of numeric ID field but doesn’t have to be.
A primary key is a column or set of columns that uniquely identifies a row in a table. It’s created on a table and ensures that the values in that column or columns must be unique and not NULL.
This is often done using some kind of numeric ID field but doesn’t have to be.
See lessWhat’s the difference between a view and a materialized view?
A view is simply an SQL query that is stored on the database, without the results. Every time a view is queried, this definition of the view’s query is run. If the underlying tables have been updated, the view will load these results. A materialized view is a query where the results have been storedRead more
A view is simply an SQL query that is stored on the database, without the results. Every time a view is queried, this definition of the view’s query is run. If the underlying tables have been updated, the view will load these results.
A materialized view is a query where the results have been stored in a permanent state, like a table. If the underlying tables are updated, then by default, the materialized views are not updated.
See lessWhat is a view? When would you use one?
A view is a database object that allows you to run a saved query to view a set of data. You create a view by specifying a SELECT query to be used as the view, and then the view can be queried just like a table. There are several reasons to use a view, such as to improve to security, create a layer oRead more
A view is a database object that allows you to run a saved query to view a set of data. You create a view by specifying a SELECT query to be used as the view, and then the view can be queried just like a table.
There are several reasons to use a view, such as to improve to security, create a layer of abstraction between the underlying tables and applications, and to simplify queries.
See lessWhat is the purpose of the IN keyword?
The IN keyword allows you to check if a value matches one of a range of values. It’s often used with subqueries that return more than one row.
The IN keyword allows you to check if a value matches one of a range of values. It’s often used with subqueries that return more than one row.
See less