These questions include SQL interview questions for freshers and experienced, as well as SQL query interview questions. 1. What is the difference between a primary key and a unique key? 2. What is a constraint, and why use constraints? 3. What is the COALESCE function? 4. What are UNION...
Constraints are those elements of the table which can be used to classify the data limit type of the table. The data limit of the table can be specified while building or changing the statement of the table. We can understand the constraints of some samples. The samples of constraints are:...
How many questions can you answer in SQL Server Interview? Take a quick Quiz to check it out Take a Quiz 3. What is a constraint, and why use constraints? SQL constraints are a set of rules applied to a column or table to maintain data integrity. SQL consists of many constraints whic...
20. What are Constraints in SQL? Constraints are used to specify the rules concerning data in the table. It can be applied for single or multiple fields in an SQL table during the creation of the table or after creating using the ALTER TABLE command. The constraints are: NOT NULL - ...
DROP – used to Delete or Drop an existing table along with its entries, constraints, triggers, indexes, and permissions. Essentially deletes the table. DROP TABLE tableName; What is Data Manipulation Language? DML or Data Manipulation Language is a set of commands that are classified pertaining...
26. What are constraints? Different types of Constraints? Constraints are the rules imposed on the database contents and processes to ensure data integrity. There are different types of constraints: Domain constraintspecifies the attribute’s domain or set of values (if we define a number column,...
Of course, reading just that is not enough, you should have tried those things to better answer the questions. Also check out the section titled "Backward Compatibility" in books online which talks about the changes that have taken place in the new version. 1. What are constraints? Explain ...
This should meet all requirements of 2NF. Removing the columns which are not dependent on primary key constraints. Fourth Normal Form (3NF):. Meeting all the requirements of third normal form and it should not have multi- valued dependencies. ...
SQL constraints are used to define guidelines for data processing and to restrict the kinds of data which can be entered into tables. Let's now examine what a default constraint is. When no other value is specified, a default limitation is used to specify a default value for a column, whi...
Constraints TheOracleServerusesconstraintstopreventinvaliddataentryintotables. Youcanuseconstraintstodothefollowing: •Enforcerulesonthedatainatablewheneverarowisinserted,updated,ordeleted fromthat table.Theconstraintmustbesatisfiedfortheoperationtosucceed. ...