One-point discovery of ORACLE indexes (Requirements for indexes for different table join statements)

One-point discovery of ORACLE indexes (Requirements for indexes for different table join statements)
Two different table join statements are written: (the same effect) www.2cto.com select * from T_FORM_ELEMENT t join t_form_resources t1 on t1.meta _ id = t. meta_id;
Select * from T_FORM_ELEMENT t, t_form_resources t1 where t. meta_id = t1.meta _ id; The PK_T_FORM_ELEMENT index is created on the meta_id field of the T_FORM_ELEMENT table. 1. alter index PK_T_FORM_ELEMENT rebuild; 2. when the index is invalid: alter index PK_T_FORM_ELEMENT unusable; Conclusion: Statement 1: select * from T_FORM_ELEMENT t join t_form_resources t1 on t1.meta _ id = t. meta_id; indexes are used no matter whether the index is valid or invalid. Statement 2: select * from T_FORM_ELEMENT t, t_form_resources t1 where t. meta_id = t1.meta _ id; if the index is invalid, no index is taken. The SQL statement syntax is different, and the index reference degree is different.