Difference between Select * and Select columnname in SQL Server

Question

hi Developers i have a simple doubt in AdoNeti have a table named TblPersonand i have the following column 1Id2Name 3Age4Genderi want to show Name and Age From the TblPerson Tablein this case i have two options1select  from TblPerson or where Some Conditions2select NameAge from TblPerson or where Some Conditionsif i use 1st one i will get all the records so no need 2nd optionbut some people using 2nd Option likeselect NameAge from TblPerson or where Some Conditionsinstead

dharmendr · Accepted Answer

Hi  paulrajmcaGiven your specification that you are selecting all columns there is little difference at this time Realize however that database schemas do change If you use SELECT  you are going to get any new columns added to the table even though in all likelihood your code is not prepared to use or present that new data This means that you are exposing your system to unexpected performance and functionality changesYou may be willing to dismiss this as a minor cost but realize that columns that you dont need still must beRead from databaseSent across the networkMarshalled into your processfor ADOtype technologies Saved in a datatable inmemoryIgnored and discarded  garbagecollectedItem 1 has many hidden costs including eliminating some potential covering index causing datapage loads and server cache thrashing incurring row  page  table locks that might be otherwise avoidedBalance this against the potential savings of specifying the columns versus an  and

Difference between Select * and Select columnname in SQL Server

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