Top 50 sql interview questions with answers – database testing interview questions sql server, mysql, oracle

Ans. Data recovery mac free Database testing is checking the integrity of actual data in the front end with the data present in the database. Data recovery phone It involves validating the data in the database, checking that there are no orphan records (record with a foreign key to a parent record that has been deleted”), no junk records are present, updating records in database and verify the value in the front end.

Ans. Database normalization An RDBMS or Relational Database Management System is a type of DBMS having relationships between the tables using indexes and different constraints like primary key, foreign key etc. Data recovery quote The use of indexes and constraints helps in faster retreival and better management of data within the databases.

Ans. Database key types The primary difference between DBMS and RDBMS is, in RDBMS we have relations between the tables of the database.


Database instance Whereas in DBMS there is no relation between the tables(data may even be stored in files).

RDBMS has primary keys and data is stored in tables. Data recovery raid 0 DBMS has no concept of primary keys with data stored in navigational or hierarchical form.

Ans. Data recovery tools SQL stands for Structured Query Language, it is an language used for creating, storing, fetching and updating of data and database objects in RDBMS.

Ans. Database programming languages SQL commands are the set of commands used to communicate and manage the data present in the database. Super 8 database The different type of SQL commands are-

Ans. 5 databases DML refers to Data Manipulation Language, it is used for managing data present in the database. H data recovery registration code Some of the DML commands are-select, insert, update, delete etc.

Ans. Database link DCL refers to Data Control Language, these commands are used to create roles, grant permission and control access to the database objects. Database google The three DCL commands are-

• Deny – Explicitly prevents a user from receiving a particular permission(e.g. Database update preventing a particular user belonging to a group to receive the access controls

Ans. Data recovery news TCL refers to Transaction Control Language, it is used to manage the changes made by DML statements. Data recovery austin These are used to process a group of SQL statements comprising a logical unit. Data recovery micro sd card The three TCL commands are-

Ans. Database relationship diagram SQL constraints are the set of rules that impose some restriction while insertion, deletion or updation of data in the databases. Data recovery services near me In SQL we have both column level as well as table level constraints which are applied at columns and tables respectively. Database worksheet Some of constraints in SQL are – Primary Key, Foreign Key, Unique Key Key, Not NULL, DEFUALT, CHECK and Index constraint.

Ans. Database constraints A primary key is a column or a combination of columns which uniquely identifies a record in the database. Database vault A primary key can only have unique and not NULL values and there can be only one primary key in a table.

Ans. Qmobile data recovery software A composite key is a primary key with multiple columns as in case of some tables a single field might not guarantee unique and not null values, so a combination of multiple fields is taken as primary key.

Ans. Tally erp 9 data recovery software A NULL value in SQL is an unknown or blank value. 7 databases in 7 weeks Since NULL is unknown value so, NULL value cannot be compared with another NULL values. 3 database models Hence we cannot use ‘=’ operator in where condition with NULL. Database programmer salary For this, we have IS NULL clause that checks if the value in field is NULL or not.

Ans. Database developer salary A foreign key is used for enforcing referential integrity in which a field marked as foriegn key in one table is linked with primary key of another table. Data recovery agent With this refrential integrity we can have only the data in foreign key which matches the data in the primary key of the other table.

Ans. Data recovery usb flash drive A check constraint is used to limit the value entered in a field. Data recovery windows E.g. Database definition we can ensure that field ‘Salary’ can only have value greater than 1000 using check constraint-

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