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Whywedefineda
metalanguageforSQL
LewisHemens
Weneedascalablesolutionformanagingdata
transformationprocessesthatworksfordataengineers,
analystsandscientists
WhyweloveSQL
SQLisgrowinginpopularitythankstomoderndatawarehouses
➔Acommonlanguagefordatadefinitionsacrossroles
➔ModernwarehouseSQLenginesscaleextremelywell
➔Easytoiterate,thanksexecutionusuallybeingone-click
➔Relativelyeasytodebug
Butithassomeproblems...
Whydoesn’tSQLscale?
It’shardtoadoptsoftwareengineeringbestpractices
➔Releaseprocesses
➔Versioncontrol
➔Unittests
➔Codereuse
Whyarethesehard,andhowcanwefixthem?
UnderstandingSQL
SQLisadeclarativequerylanguage
DeclarativeprogrammingImperativeprogramming
WhenyousaywhatyouwantWhenyousayhowtoget
whatyouwant
Advantagesofbeingdeclarative
ThefactthatSQLisdeclarativemeansithasmanybenefits
➔SQLqueriescanbeparallelized
➔SQLqueriescanbeautomaticallyoptimized
➔FormostSQLstatementstherearenosideeffects
➔SQLqueriesareguaranteedtoeventuallyterminate
SQLisnotaprogramminglanguage
SQLisfewfeaturesshortofbeingaprogramminglanguage
➔SQLhaslittleifanycontrolflow
➔Thereisnorecursionoriteration*
➔SQLisdeclarativeandstatic
*SomeflavorsofSQL(e.g.T-SQL)addtheseandareturingcomplete
Example:writingreusablecode
select
floor(age/5)*5asage_group,
count(1)asuser_count
fromusers
groupbyage_group
Example:writingreusablecode
select
floor(age/5)*5asage_group,
count(1)asuser_count
fromusers
groupbyage_group
Wecan’treusethisquery:
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