Key in SQL can be defined as the subset of the columns present in tables which permit to uniquely identify a row. Every row in a table will have unique value for key. Keys are used to fetch records from a table according to the given condition. The different types of key used to retrieve […]
What is Database Transaction?
Database transaction can be defined as the separate actions which are in either processed or yet to be processed state. All or Nothing is the defining feature of a database transaction. Each and every database transaction will contain several SQL statements. The common database transaction scenario can be noted using the acronym ACID. How to […]
What is Database Locking?
Database lock can be used to restrict the access certain data to some particular user/session. The database locking is most commonly used to prevent updating same data by two or more different users. Database locking are usually done using ROLLBACK or COMMIT SQL statements. When a user/session is updating a data; it will be kept […]
What is Database Deadlock?
Database deadlock can be defined as a situation when a data is locked by two or more data sessions. The lock on a particular data is requested by the database session. Each lock used on a database is entirely different from others. The time of the database sessions waiting to force the database lock is […]
What is Data Cardinality?
Cardinality in structured query language (SQL) can be defined as the mean of unique data value present in certain column. Cardinality is also known as data cardinality or attribute of database table. There are three types of data cardinality High Data Cardinality Normal Data Cardinality Low Data Cardinality Read: All about SQL CREATE USER Query […]
What is Cost Based Optimizer?
Query optimizer in RDBMS can be defined as a part of SQL program which is used to analyze the best way to run a SQL query. The query optimizers are used to improve the efficiency of the SQL statements. Related: SQL & .NET Interview questions and Answers What is Cost based Optimizer? Cost based optimizer […]
What is Clustered Index?
Clustered index in a database can be defined as the order in which rows present in a table are stored. Clustered indexes are used to accelerate the query searches in the database. It is easier to identify the data if rows are arranged in a proper manner. Read: Clustered & Non-clustered index in SQL Example […]
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