数据库 字段 数据类型的疑问？

[wbdx]

某字段作为标记

可以 VARCHAR(1)，也可以NUMBER(1)

1。哪一种更加节省空间，效率最高？
2。选择的理由和依据是什么？

[xmankevin1980xman]

number(1)高些，也节省空间。首先，比如VARCHAR（4）你输入1个字符，剩下的它用空格补足。而NUMBER就没此种情况.

[bobfang]

只是做为标记用，可以用char(1)

[loveme820]

number(1)，众所周知，数字型查询速度快，占用空间小。

[wbdx]

to bobfang(匆匆过客)

NUMBER(1) 有什么不好???

[bobfang]

char(1)并且not null是最省空间的。可以做这样的测试：
create table t_test1(
col3 char(1) not null,
col4 char(1) not null,
col5 char(1) not null,
col6 char(1) not null,
col7 char(1) not null,
col8 char(1) not null,
col9 char(1) not null
)
/
create table t_test2(
col3 number(1) not null,
col4 number(1) not null,
col5 number(1) not null,
col6 number(1) not null,
col7 number(1) not null,
col8 number(1) not null,
col9 number(1) not null
)
/

insert into t_test1 select '1','1','1','1','1','1','1' from all_tab_columns order by table_name,column_id;
insert into t_test2 select 1,1,1,1,1,1,1 from all_tab_columns order by table_name,column_id;
commit;
insert into t_test1 select * from t_test1;
insert into t_test1 select * from t_test1;
commit;
insert into t_test2 select * from t_test2;
insert into t_test2 select * from t_test2;
commit;
analyze table t_test1 compute statistics;
analyze table t_test2 compute statistics;
select segment_name,bytes from user_segments where segment_name like 'T_TEST%';
select table_name,NUM_ROWS,BLOCKS,AVG_ROW_LEN from user_tables where table_name like 'T_TEST%';