Cursor is a database object used by applications to manipulate data in a set on a row‐by‐row basis, instead of the typical SQL commands that operate on all the rows in the set at one time.
In order to work with a cursor we need to perform some steps in the following order
Declare cursor,
Open cursor,
Fetch row from the cursor,
Process fetched row,
Close cursor,
Deallocate cursor.
What Is Collation?
The physical storage of character strings in SQL Server is controlled by collations. A collation specifies the bit patterns that represent each character and the rules by which characters are sorted and compared.
What Is Difference Between Function And Stored Procedure?
UDF can be used in the SQL statements anywhere in the WHERE/HAVING/SELECT section where as Stored procedures cannot be. UDF's that return tables can be treated as another rowset. This can be used in JOIN's with other tables. Inline UDF's can be thought of as views that take parameters and can be used in JOINs and other Rowset operations.
What Is Sub-query? Explain Properties Of Sub-query?
Sub‐queries are often referred to as sub‐selects, as they allow a SELECT statement to be executed arbitrarily within the body of another SQL statement. A sub‐query is executed by enclosing it in a set of parentheses. Sub‐queries are generally used to return a single row as an atomic value, though they may be used to compare values against multiple rows with the IN keyword.
A sub query is a SELECT statement that is nested within another T‐SQL statement. A sub query SELECT statement if executed independently of the T‐SQL statement, in which it is nested, will return a resultset. Meaning a subquery SELECT statement can standalone and is not depended on the statement in which it is nested. A subquery SELECT statement can return any number of values, and can be found in the column list of a SELECT statement, a FROM, GROUP BY, HAVING, and/or ORDER BY clauses of a T‐SQL statement. A Subquery can also be used as a parameter to a function call. Basically a subquery can be used anywhere an expression can be used.
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What Are Different Types Of Join?
Cross Join
A cross join that does not have a WHERE clause produces the Cartesian product of the tables involved in the join. The size of a Cartesian product result set is the number of rows in the first table multiplied by the number of rows in the seond table. The common example is when company wants to combine each product with a pricing table to analyze each product at each price.
Inner Join
A join that displays only the rows that have a match in both joined tables is known as inner Join. This is the default type of join in the Query and View Designer.
Outer Join
A join that includes rows even if they do not have related rows in the joined table is an Outer Join. You can create three different outer join to specify the unmatched rows to be included
Left Outer Join
In Left Outer Join all rows in the first‐named table i.e. "left" table, which appears leftmost in the JOIN clause are included. Unmatched rows in the right table do not appear.
Right Outer Join
In Right Outer Join all rows in the second‐named table i.e. "right" table, which appears rightmost in the JOIN clause are included. Unmatched rows in the left table are not included.
Full Outer Join
In Full Outer Join all rows in all joined tables are included, whether they are matched or not.
Self Join
This is a particular case when one table joins to itself, with one or two aliases to avoid confusion. A self join can be of any type, as long as the joined tables are the same. A self join is rather unique in that it involves a relationship with only one table. The common example is when company has a hierarchal reporting structure whereby one member of staff reports to another. Self Join can be Outer Join or Inner Join.
What Are Primary Keys And Foreign Keys?
Primary keys are the unique identifiers for each row. They must contain unique values and cannot be null. Due to their importance in relational databases, Primary keys are the most fundamental of all keys and constraints. A table can have only one Primary key.
Foreign keys are both a method of ensuring data integrity and a manifestation of the relationship between tables.
What Is User Defined Functions? What Kind Of User-defined Functions Can Be Created?
User‐Defined Functions allow defining its own T‐SQL functions that can accept 0 or more parameters and return a single scalar data value or a table data type.
Different Kinds of User‐Defined Functions created are
Scalar User‐Defined Function
A Scalar user‐defined function returns one of the scalar data types. Text, ntext, image and timestamp data types are not supported. These are the type of user‐defined functions that most developers are used to in other programming languages. You pass in 0 to many parameters and you get a return value.
Inline Table‐Value User‐Defined Function
An Inline Table‐Value user‐defined function returns a table data type and is an exceptional alternative to a view as the user‐defined function can pass parameters into a T‐SQL select command and in essence provide us with a parameterized, non‐updateable view of the underlying tables.
Multi‐statement Table‐Value User‐Defined Function
A Multi‐Statement Table‐Value user‐defined function returns a table and is also an exceptional alternative to a view as the function can support multiple T‐SQL statements to build the final result where the view is limited to a single SELECT statement. Also, the ability to pass parameters into a T-SQL select command or a group of them gives us the capability to in essence create a paameterized, non‐updateable view of the data in the underlying tables. Within the create function command you must define the table structure that is being returned. After creating this type of user‐defined function, It can be used in the FROM clause of a T‐SQL command unlike the behavior found when using a stored procedure which can also return record sets.
What Is Identity?
Identity (or AutoNumber) is a column that automatically generates numeric values. A start and increment value can be set, but most DBA leave these at 1. A GUID column also generates numbers; the value of this cannot be controlled. Identity/GUID columns do not need to be indexed.
What Is Datawarehousing?
Subject‐oriented, meaning that the data in the database is organized so that all the data elements relating to the same real‐world event or object are linked together;
Time‐variant, meaning that the changes to the data in the database are tracked and recorded so that reports can be produced showing changes verSUS time;
Non‐volatile, meaning that data in the database is never over‐written or deleted, once committed, the data is static, read‐only, but retained for future reporting.
integrated, meaning that the database contains data from most or all of an organization's operational applications, and that this data is made consistent.
Which Tcp/ip Port Does Sql Server Run On? How Can It Be Changed?
SQL Server runs on port 1433. It can be changed from the Network Utility TCP/IP properties –> Port number, both on client and the server.
What Are The Difference Between Clustered And A Non-clustered Index?
A clustered index is a special type of index that reorders the way records in the table are physically stored. Therefore table can have only one clustered index. The leaf nodes of a clustered index contain the data pages.
A non clustered index is a special type of index in which the logical order of the index does not match the physical stored ordr of the rows on disk. The leaf node of a non clustered index does not consist of the data pages. Instead, the leaf nodes contain index rows.
What Are The Different Index Configurations A Table Can Have?
A table can have one of the following index configurations
No indexes,
A clustered index,
A clustered index and many nonclustered indexes,
A nonclustered index,
Many nonclustered indexes.
What Are Different Types Of Collation Sensitivity?
Case sensitivity ‐ A and a, B and b, etc.
Accent sensitivity ‐ a and á, o and ó, etc.
Kana Sensitivity ‐ When Japanese kana characters Hiragana and Katakana are treated differently, it is called Kana sensitive.
Width sensitivity ‐ A single‐byte character (half‐width) and the same character represented as a double‐byte character (full‐width) are treated differently than it is width sensitive.
What Is Oltp (online Transaction Processing)?
In OLTP ‐ online transaction processing systems relational database design use the discipline of data modeling and generally follow the odd rules of data normalization in order to ensure absolute data integrity. Using these rules complex information is broken down into its most simple structures (a table) where all of the individual atomic level elements relate to each other and satisfy the normalization rules.
What Iss The Difference Between A Primary Key And A Unique Key?
Both primary key and unique key enforces uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where are unique creates a nonclustered index by default. Another major difference is that, primary key doesn't allow NULL's, but unique key allows one NULL only.
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