SQL Data Cleaning

Author: ellaclauz

warehouse Data Cleaning.sql

@@ -0,0 +1,23 @@
+-- data cleaning
+-- check for missing values
+
+select *
+from project 
+where year is null or month is null or supplier is null or itemcode is null 
+or itemdescription is null or itemtype is null or retailsales is null or retailtransfers is null
+or warehousesales is null;
+
+-- check for duplicates
+
+select year, month, supplier, itemcode, itemdescription, itemtype, retailsales, retailtransfers, warehousesales
+from project 
+group by year, month, supplier, itemcode, itemdescription, itemtype, retailsales, retailtransfers, warehousesales
+having count(*) > 1;
+
+/* removing rows with missing values
+since it is less than 1% of the whole dataset */
+
+delete from project 
+where year is null or month is null or supplier is null or itemcode is null 
+or itemdescription is null or itemtype is null or retailsales is null or retailtransfers is null
+or warehousesales is null;