"=" And "" in Oracle

In Oracle, equal is =, not equal is! = And <>

 

1. 1 <> 1:

It is used to retrieve only structures without data. For example:

Create Table table_temp tablespace tbs_temp

Select * From table_ori where
1<>1

Create a table table_temp with the same table_ori structure, but do not use data in table_ori.

 

2.1 = 1 is used to create dynamic SQL:

For example:

Lv_string = 'select tbl_name, tbl_desc from tbl_test where1 = 1' + condition;

When you select the query name 'abc ',

Condition = 'and tbl_name = ''abc ''';

However, when the user does not select a name for query, the condition is an empty string ''.

Lv_string = 'select tbl_name, tbl_desc from tbl_test where1 = 1 ',

No error occurs during running, which is equivalent to no restriction on name conditions. However, if there is no 1 = 1 condition

Lv_string = 'select tbl_name, tbl_desc from tbl_test where ';

In this way, an error is reported.