### Arithmetic aggregation operators in MongoDB

\$abs: \$abs returns absolute value of the number.

\$add: \$add use to summation numbers and date it returns same as added number and new added date. If you are adding date mean first expression is date and second then second expression (number) treats as millisecond. \$add accept any number of expression.

\$ceil: \$ceil returns the smallest integer greater than or equal to the specified number.

\$divide: \$divide returns the result of dividing the first number by the second. \$divide accepts two argument expressions.

\$exp: \$exp Euler’s number (i.e. e ) to the specified exponent and returns the result.

\$floor: \$floor returns the largest integer less than or equal to the specified number.

\$ln: \$ln calculates the natural log of a number.

\$log: \$log calculates the log of a number in the specified base.

\$log10:\$log10 calculates the log base 10 of a number.

\$mod:\$mod returns the remainder of the first number divided by the second. \$mod accepts two argument expressions.

\$multiply: \$multiply multiplies numbers to return the product. \$multiply  accepts any number of argument expressions.

\$pow: \$pow raises a number to the specified exponent.

\$sqrt: \$sqrt calculates the square root.

\$subtract: \$subtract returns the result of subtracting the second value from the first. If the two values are numbers, return the difference. If the two values are dates, return the difference in milliseconds. If the two values are a date and a number in milliseconds, return the resulting date. \$subtract accepts two argument expressions. If the two values are a date and a number, specify the date argument first as it is not meaningful to subtract a date from a number.

\$trunc:\$trunc truncates a number to its integer.

### What is difference between UNION and UNION ALL in SQL Server

We use UNION and UNION ALL operator to combine multiple results set into one result set.
UNION operator is used to combining multiple results set into one result set but removes any duplicate rows. Basically, UNION is used to performing a DISTINCT operation across all columns in the result set. UNION operator has the extra overhead of removing duplicate rows and sorting result.
UNION ALL operator use to combine multiple results set into one result set but it does not remove any duplicate result. Actually, this does not remove duplicate rows so it is faster than the UNION operator. If you want to combine multiple results and without duplicate records then use UNION otherwise UNION ALL is better.
Following some rules for using UNION/UNION ALL operator
1.The number of the column should be the same in the query's when you want to combine them. 2.The column should be of the same data type. 3.ORDER BY clause can be applied to the overall result set not within each result set.
4.Column name of …

### Dropdownlist selectedindexchanged event is not firing

<asp:DropDownList ID="ddlSource" runat="server" DataSourceID="SqlDataSource1" DataTextField="vcSuplierNm" ViewStateMode="Enabled DataValueField="vcSuplierCode" EnableViewState="true" AppendDataBoundItems="true" OnSelectedIndexChanged="ddl_OnSelectedIndexChanged" AutoPostBack="true"></asp:DropDownList>

in drop DropDownList

### How to get first & last day of the previous month

This query will return first day of the previous month

### Remove special characters from string in SQL server

I faced many times an issue to remove special characters from a string. Suppose you are working on searching concept and you have to remove the special characters from search string due to query performance, there are many solution are available but T-SQL is easily resolved this issue.

DECLARE@strVARCHAR(400) DECLARE@expresVARCHAR(50)='%[~,@,#,\$,%,&,*,(,),.,!]%' SET@str='(remove) ~special~ *characters. from string in sql!' WHILEPATINDEX(@expres,@str)> 0 BEGIN SET@str=Replace(REPLACE(@str,SUBSTRING(@str,PATINDEX(@expres,@str), 1 ),''),'-',' ') END SELECT@str

### Add day to ISODate in MongoDB

We can use \$add operator to add days in ISODate in mongodb, \$add is the Arithmetic Aggregation Operator which adds number and date in mongodb.
Syntax:

{ \$add: [ <expression1>, <expression2>, ... ] }

Note:  If one of the argument is date \$add operator treats to other arguments as milliseconds to add to the date.
Example: Suppose we have a Test collection as below.

{"Title" : "Add day to ISODate in MongoBD","CreatedDate" : ISODate("2016-07-07T08:00:00.000Z")}

Query to add 2 days in CreatedDate

db.Test.aggregate([      { \$project: { Title: 1, AddedDate: { \$add: [ "\$CreatedDate", 2*24*60*60000 ] } } }    ])

Result:

{ "_id" : ObjectId("579a1567ac1b3f3732483de0"), "Title" : "Add day to ISODate in MongoBD", "AddedDate" : ISODate("2016-07-09T08:00:00.000Z") }

Note: As mentioned in above note we have to convert days in millisecond because \$add operator treat to other arg…

### Remove special character from string in MongoDB

Problem: Suppose wehave a collection and one field is type string contains some special character (like !@#\$%) and we don’t want these special character.
Solution: We can easily remove the special character from field using script “replace(/[^a-zA-Z 0-9 ]/g, '')” in our query.  How can we remove special character from string using this script please see following example.
Example: Suppose we have a collection “EduSurvey “where we are collecting information from institutions.

{Name:"JB institute”, About:"This is good one collage for MBA", Information:"This \$%%institute ##has good faculty etc\$\$"}
{Name:"MK institute”, About:"This is good one collage for MCA", Information:"This\$\$%# is the dummy text12"}
{Name:"MG institute”, About:"This is good one collage for B,Tech", Information:"This# institute@ has&* good infrastructure"}

Did you notice Information fields contains some special character so we…

### \$group (aggregation) in MongoDB

IF we want to group document by specific expression and want to output for each distinct grouping of document here we have to use \$group. IF you familiar with Relational Database like SQL Server, It's work same like GROUP BY clause.
Output document contains the _id field which contains the distinct group by key also output document contains computed fields which grasp the value of some accumulator expression grouped by the _id.
Syntax:

{ \$group: { _id: <expression>, <field1>: { <accumulator1> : <expression1> }, ... }

Accumulator Operator:
\$num : It's returns sum of the numeric value. It can be use in \$project also in mongodb 3.2 version.
\$avg  : It's returns the average of numeric values. It can be use in \$project also in mongodb 3.2 version.
\$first : It's returns a value from the first document for each group.
\$last : It's returns a value from the first document for each group.
\$max : It's returns the highest expression value for each group.…

### Add a column, with a default value, to an existing table in SQL Server

You can do it by edit of table design, if you want do it with query see following.
Syntax: