understanding exists operator use in multi row sub query

Author: techysanoj

multi_row_sub_query_using_exist_operator.sql

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+use techysanoj;
+
+show tables;
+
+select* from ecommerce_sales_large limit 10;
+select max(quantity) from ecommerce_sales_large;
+
+-- sub query
+select * from ecommerce_sales_large where quantity > 3;
+
+
+select * 
+from ecommerce_sales_large 
+where exists 
+(select * 
+from ecommerce_sales_large 
+where quantity > 3);
+
+-- exist means if the inner query returns any no of row (means simply run) 
+-- then the outer query will work else it will not
+
+
+select * 
+from ecommerce_sales_large 
+where exists 
+(select * 
+from ecommerce_sales_large 
+where quantity > 5); -- now this will not be having any output because inner query return 0 rows.