Q1: What indexes would you recommend to be added to improve its performance?
Maybe: CREATE INDEX index_Analyte_LabAnalyteData ON LabAnalyteData (Analyte);
But what if I add the following index; is there still a need to add additional indexes?
CREATE INDEX index_FK_IDinAccess_LabAnalyteData ONLabAnalyteData (IDinAccess, AnalyteCode, Analyte, ConcentrationLevelUnit);
Means how many times you ran the query. Trial 2 used the cache since data still accessible from Trial 1.