ServiceNow Most Frequently Asked Latest MySQL Interview Questions Answers
What Are The Different Table Present In Mysql?
MyISAM : This is default. Based on Indexed Sequntial Access Method. The above SQL will create a MyISA table.
ISAM : same
HEAP : Fast data access, but will loose data if there is a crash. Cannot have BLOB, TEXT & AUTO INCRIMENT fields
BDB : Supports Transactions using COMMIT & ROLLBACK. Slower that others.
InoDB : same as BDB
What Is Primary Key?
A primary key is a single column or multiple columns defined to have unique values that can be used as row identifications.
What Is Foreign Key?
A foreign key is a single column or multiple columns defined to have values that can be mapped to a primary key in another table.
What Is Index?
An index is a single column or multiple columns defined to have values pre-sorted to speed up data retrieval speed.
What Is Join?
Join is data retrieval operation that combines rows from multiple tables under certain matching conditions to form a single row.
What Is Union?
Join is data retrieval operation that combines multiple query outputs of the same structure into a single output. By default the MySQL UNION removes all duplicate rows from the result set even if you don’t explicit using DISTINCT after the keyword UNION.
SELECT customerNumber id, contactLastname name
FROM customers
UNION
SELECT employeeNurrber id, firstname name
FROM employees
id name
103 Schmitt
112 King
114 Ferguson
119 Labrune
121 Bergulfsen
What Is Isam?
ISAM (Indexed Sequential Access Method) was developed by IBM to store and retrieve data on secondary storage systems like tapes.
What Is Innodb?
lnnoDB is a transaction safe storage engine developed by Innobase Oy (an Oracle company now).
What Is Bdb (berkeleydb)?
BDB (BerkeleyDB) is transaction safe storage engine originally developed at U.C. Berkeley. It is now developed by Sleepycat Software, Inc. (an Oracle company now).
What Is Csv?
CSV (Comma Separated Values) is a file format used to store database table contents, where one table row is stored as one line in the file, and each data field is separated with comma.
What Is Transaction?
A transaction is a logical unit of work requested by a user to be applied to the database objects. MySQL server introduces the transaction concept to allow users to group one or more SQL statements into a single transaction, so that the effects of all the SQL statements in a transaction can be either all committed (applied to the database) or all rolled back (undone from the database).
What Is Commit?
Commit is a way to terminate a transaction with all database changes to be saved permanently to the database server.
What Is Rollback?
Rollback is a way to terminate a transaction with all database changes not saving to the database server.
How Many Groups Of Data Types?
MySQL support 3 groups of data types as listed below:
String Data Types - CHAR, NCHAR, VARCHAR, NVARCHAR, BINARY, VARBINARY, TINYBLOB, TINYTEXT, BLOB, TEXT, MEDIUMBLOB, MEDIUMTEXT, LONGBLOB, LONGTEXT, ENUM, SET.
Numeric Data Types - BIT, TINYINT, BOOLEAN, SMALLINT, MEDIUMINT, INTEGER, BIGINT, FLOAT, DOUBLE, REAL, DECIMAL.
Date and Time Data Types - DATE, DATETIME, TIMESTAMP, TIME, YEAR.
What Are The Different Table Present In Mysql?
MyISAM : This is default. Based on Indexed Sequntial Access Method. The above SQL will create a MyISA table.
ISAM : same
HEAP : Fast data access, but will loose data if there is a crash. Cannot have BLOB, TEXT & AUTO INCRIMENT fields
BDB : Supports Transactions using COMMIT & ROLLBACK. Slower that others.
InoDB : same as BDB
What Is Primary Key?
A primary key is a single column or multiple columns defined to have unique values that can be used as row identifications.
What Is Foreign Key?
A foreign key is a single column or multiple columns defined to have values that can be mapped to a primary key in another table.
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| ServiceNow Most Frequently Asked Latest MySQL Interview Questions Answers |
What Is Index?
An index is a single column or multiple columns defined to have values pre-sorted to speed up data retrieval speed.
What Is Join?
Join is data retrieval operation that combines rows from multiple tables under certain matching conditions to form a single row.
What Is Union?
Join is data retrieval operation that combines multiple query outputs of the same structure into a single output. By default the MySQL UNION removes all duplicate rows from the result set even if you don’t explicit using DISTINCT after the keyword UNION.
SELECT customerNumber id, contactLastname name
FROM customers
UNION
SELECT employeeNurrber id, firstname name
FROM employees
id name
103 Schmitt
112 King
114 Ferguson
119 Labrune
121 Bergulfsen
What Is Isam?
ISAM (Indexed Sequential Access Method) was developed by IBM to store and retrieve data on secondary storage systems like tapes.
What Is Innodb?
lnnoDB is a transaction safe storage engine developed by Innobase Oy (an Oracle company now).
What Is Bdb (berkeleydb)?
BDB (BerkeleyDB) is transaction safe storage engine originally developed at U.C. Berkeley. It is now developed by Sleepycat Software, Inc. (an Oracle company now).
What Is Csv?
CSV (Comma Separated Values) is a file format used to store database table contents, where one table row is stored as one line in the file, and each data field is separated with comma.
What Is Transaction?
A transaction is a logical unit of work requested by a user to be applied to the database objects. MySQL server introduces the transaction concept to allow users to group one or more SQL statements into a single transaction, so that the effects of all the SQL statements in a transaction can be either all committed (applied to the database) or all rolled back (undone from the database).
What Is Commit?
Commit is a way to terminate a transaction with all database changes to be saved permanently to the database server.
What Is Rollback?
Rollback is a way to terminate a transaction with all database changes not saving to the database server.
How Many Groups Of Data Types?
MySQL support 3 groups of data types as listed below:
String Data Types - CHAR, NCHAR, VARCHAR, NVARCHAR, BINARY, VARBINARY, TINYBLOB, TINYTEXT, BLOB, TEXT, MEDIUMBLOB, MEDIUMTEXT, LONGBLOB, LONGTEXT, ENUM, SET.
Numeric Data Types - BIT, TINYINT, BOOLEAN, SMALLINT, MEDIUMINT, INTEGER, BIGINT, FLOAT, DOUBLE, REAL, DECIMAL.
Date and Time Data Types - DATE, DATETIME, TIMESTAMP, TIME, YEAR.
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