How to write a sql statement to find the first occurrence of a non zero value?
There is a slight chance the column “a” has a value of 0 which is not null. In that case, you?ll loose the information. There is another way of searching the first not null value of a column: select column_name from table_name where column_name is not null and rownum<2; Question: What is normalazation, types with e.g.\'s. _ with queries of all types Answer: There are 5 normal forms. It is necessary for any database to be in the third normal form to maintain referential integrity and non-redundancy. First Normal Form: Every field of a table (row, col) must contain an atomic value Second Normal Form: All columns of a table must depend entirely on the primary key column. Third Normal Form: All columns of a table must depend on all columns of a composite primary key. Fourth Normal Form: A table must not contain two or more independent multi-valued facts. This normal form is often avoided for maintenance reasons. Fifth Normal Form: is about symmetric dependencies. Each normal form assumes t
