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How To Compare Engagement Inwards Sql Server Query? Finding All Rows Betwixt Ii Dates

It's tricky to utilization dates inwards SQL server query, especially if you lot don't pick out practiced noesis of how DateTime type plant inwards SQL server. For example, i of the frequently asked SQL queries on the interview is to "select all rows where the appointment is 20151007?" How would you lot produce that? Does next SQL Query volition operate correctly

select * from tabular array where appointment = '20151007'

It may or may not, it entirely depends on upon information inwards your table. When you lot only furnish appointment constituent of a DateTime variable, it uses '00:00:00.000' for fourth dimension part.

So if you lot pick out whatever row which has the same appointment but dissimilar fourth dimension as well as then this query volition non work. For example, you lot pick out the Order tabular array where you lot pick out 2 orders, i alongside order_date='20150107' as well as other alongside order_date='20150107:01:00:00:000', as well as then higher upwardly query volition only render root order.  I'll explicate how to discovery rows betwixt dates inwards SQL Server inwards petty to a greater extent than particular inwards this article.

Many Java or C++ programmer who uses SQL Server doesn't pay plenty attending to the information type of appointment columns e.g. order_date, trade_date etc as well as many of them don't fifty-fifty know that how SQL Server volition compare their status alongside the information inwards that column. It's non surprising because for them SQL is secondary skill, piece C++ or Java is top dog skill, but, to move honest in that place would move really few existent the world application where you lot don't pick out to operate on SQL.

So, if you lot similar to better your noesis of SQL fundamentals, specially inwards SQL Server, I propose you lot read Microsoft SQL Server 2012 T-SQL Fundamentals to larn to a greater extent than nigh DATE, TIME as well as DATETIME information types. I pick out referred that mass earlier writing this article as well as it helped me immensely to create sum the gap inwards my knowledge.

Query alongside Comparing Dates inwards SQL

In fellowship to sympathise how dates are compared inwards SQL, let's meet an event where DateTime champaign pick out simply about fourth dimension values equally well.

Suppose nosotros pick out the next tabular array alongside a varchar course_name as well as datetime course_date columns:

IF OBJECT_ID( 'tempdb..#Course' ) IS NOT NULL DROP TABLE #Course;  CREATE TABLE #Course (course_name varchar(10), course_date datetime);  INSERT INTO #Course VALUES ('Java', '2015-10-06 11:16:10.496'); INSERT INTO #Course VALUES ('MySQL', '2015-10-07 00:00:00.000'); INSERT INTO #Course VALUES ('SQL SERVER', '2015-10-07 11:26:10.193' ); INSERT INTO #Course VALUES ('PostgreSQL', '2015-10-07 12:36:10.393'); INSERT INTO #Course VALUES ('Oracle', '2015-10-08 00:00:00.000');

Now, you lot demand to write a query to get all courses which are on '2015-10-07'? Right query, should render 3 rows containing dates starting alongside '2015-1-07', equally shown below:

'MySQL',      '2015-10-07 00:00:00.000' 'SQL SERVER', '2015-10-07 11:26:10.193' 'PostgreSQL', '2015-10-07 12:36:10.393'

Let's meet how dissimilar solution works:

If you lot just compare dates alongside = operator as well as only provides date, you lot volition acquire the rows where fourth dimension champaign is null because SQL server volition utilization '00:00:00.000" for time, equally seen inwards the next event :

SELECT * FROM #Course WHERE course_date = '2015-10-07' course_name course_date MySQL 2015-10-07 00:00:00.000

You tin meet it only brings i row, where fourth dimension is zero, it didn't stand upwardly for the other 2 rows where fourth dimension is non-zero. See Querying Microsoft SQL Server 2012 to larn to a greater extent than nigh how SQL server handles appointment formats as well as missing appointment as well as fourth dimension information.

Solution 2 - Comparing dates alongside betwixt clause

It seems between is the right selection to compare dates without times. You tin set electrical flow appointment as well as side yesteryear side appointment to encompass all times where the appointment is same, but unfortunately that volition non work. It volition equally good pick out receive of the side yesteryear side appointment value equally seen below:

SELECT * FROM #Course WHERE course_date betwixt '2015-10-07' as well as '2015-10-08' course_name course_date MySQL       2015-10-07 00:00:00.000 SQL SERVER  2015-10-07 11:26:10.193 PostgreSQL  2015-10-07 12:36:10.393 Oracle      2015-10-08 00:00:00.000

You tin meet betwixt equally good fetched 2015-10-08 00:00:00.000 values, which is non desirable. This happens because BETWEEN clause volition always pull whatever values of side yesteryear side appointment midnight.  See Querying Microsoft SQL Server 2012 to larn to a greater extent than on this topic. The give-and-take is valid for SQL Server 2014 equally well.

Always Use >= as well as < to compare dates

The right reply is to utilization the greater than (>) as well as less than (<) operators. This volition operate equally expected. In fellowship to utilization this option, simply set the appointment as well as side yesteryear side appointment inwards where clause equally shown below:

SELECT * FROM #Course WHERE course_date >= '2015-10-07' as well as course_date < '2015-10-08' course_name course_date MySQL       2015-10-07 00:00:00.000 SQL SERVER  2015-10-07 11:26:10.193 PostgreSQL  2015-10-07 12:36:10.393

You tin meet we got precisely 3 3 rows equally expected. Just recall to utilization < on the mo predicate, this volition ensure that  '2015-10-08 00:00:00.000' volition non acquire picked up.

That's all nigh how to compare appointment columns inwards SQL Server. You tin meet that it's really slow to acquire the SQL query alongside appointment incorrect. Sometimes you lot experience your query is working fine but it failed inwards the existent environment, Why? because of dissimilar information inwards both environment. In QA if you lot don't pick out whatever midnight appointment value as well as then the appointment alongside betwixt clause volition operate fine but if you lot a midnight value inwards the existent environs it volition fail.

The right agency to compare appointment only values alongside a DateTime column is yesteryear using <= as well as > condition. This volition ensure that you lot volition acquire rows where appointment starts from midnight as well as ends earlier midnight e.g. dates starting alongside '00:00:00.000' as well as ends at "59:59:59.999".

Also worth remembering is that when you lot produce date = '2015-10-08' as well as if the appointment is DateTime column as well as then SQL Server volition utilization '2015-10-08 00:00:00.000' value. So delight aware of that. Btw, if you lot desire to do challenging SQL queries as well as then you lot tin equally good check Joe Celko's SQL Puzzles as well as Answers, Second Edition, i of the interesting books to better SQL skill.

Other SQL Server articles you lot may like

• How to bring together 3 tables inwards i SQL Query? (tutorial)
• How to delete from a tabular array using bring together inwards SQL? (tutorial)
• How to supplant zip alongside empty String inwards SQL Server? (solution)
• Difference betwixt WHERE as well as HAVING clause inwards SQL? (answer)
• How to add together columns on existing tabular array inwards Microsoft SQL Server? (solution)
• Difference betwixt row_number(), rank(), as well as dense_rank() inwards SQL? (answer)
• How to growth the length of existing varchar column inwards SQL Server? (solution)
• How to acquire simply appointment or fourth dimension from GETDATE() purpose inwards SQL Server? (answer)
• Difference between SQL queries inwards Oracle as well as Microsoft SQL Server? (answer)
• How to discovery the length of String inwards MSSQL? (solution)
• SQL query to discovery all tabular array names inwards a database? (query)

Further Learning
Introduction to SQL
The Complete SQL Bootcamp
SQL for Newbs: Data Analysis for Beginners

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