num_rows 不显示值

create table t1(id int,name varchar(20));

insert into t1 values(1,'tom');

SQL> select num_rows,table_name from user_tables;

  NUM_ROWS TABLE_NAME
---------- ------------------------------
           T1
//收集一下统计信息，就可以看到了
SQL> CALL DBMS_STATS.GATHER_TABLE_STATS ('AAA','T1');

SQL> select num_rows,table_name from user_tables;

  NUM_ROWS TABLE_NAME
---------- ------------------------------
         1 T1