A candidate key is one that can identify each row of a table uniquely. Generally a candidate key becomes the primary key of the table. If the table has more than one candidate key, one of them will become the primary key, and the rest are called alternate keys.
Cursors allow row-by-row precessing of the result-sets. Types of cursors: Static, Dynamic, Forward-only, Keyset-driven. Disadvantages of cursors: Each time you fetch a row from the cursor, it results in a network roundtrip, where as a normal SELECT query makes only one rowundtrip, however large the resultset is. Cursors are also… Continue reading
Suppose we have a table in which a column has Auto-incremented and its value automatically increases on every row. This increasing is depends on the seed and incrementing value. Let us create a table with an auto-increment identity column : CREATE TABLE [TableName] ( [ID] [int] IDENTITY(1,1) NOT NULL, [UserName]… Continue reading
How to find highest 3 salary in sql? Select top 1 sal from tbl where sal in(select top 3 sal from tbl order by sal desc) order by sal asc. How to find Duplicate entries in sql? Select distinct(sal) from tbl group by sal having count(*)>1; How to delete Duplicate… Continue reading
In SQL Server 2000 the Query Analyzer and Enterprise Manager are separate, whereas in SQL Server 2005 both were combined as Management Studio. In Sql 2005,the new datatype XML is used,whereas in Sql 2000 there is no such datatype In Sql server2000 we can create 65,535 databases,whereas in Sql server2005… Continue reading
A data warehouse is a collection of data gathered and organized so that it can easily by analyzed, extracted, synthesized, and otherwise be used for the purposes of further understanding the data.
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… Continue reading
An isolation level determines the degree of isolation of data between concurrent transactions. The default SQL Server isolation level is Read Committed. A lower isolation level increases concurrency, but at the expense of data correctness. Conversely, a higher isolation level ensures that data is correct, but can affect concurrency negatively…. Continue reading
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… Continue reading
SELECT * FROM tbl SELECT COUNT(*) FROM tbl SELECT rows FROM sysindexes WHERE id=OBJECT_ID(tbl) AND indid<2