在Oracle 9i上查询ALL_TAB_COLS视图时，它会列出标记为UNUSED的列以及“活动”表列。似乎没有明确说明列是否为UNUSED的字段，或者我可以加入的任何视图列出表中未使用的列。如何轻松找出未使用的列，以便我可以从ALL_TAB_COLS中过滤掉它们？
答案 0 :(得分：2)
尝试使用ALL_TAB_COLUMNS而不是ALL_TAB_COLS。在Oracle 11.2中，我发现未使用的列出现在ALL_TAB_COLS中（虽然已重命名）但不在ALL_TAB_COLUMNS中。
我创建了一个这样的表：
create table t1 (c1 varchar2(30), c2 varchar2(30);
然后设置c2 unused：
alter table t1 set unused column c2;
然后我看到了：
select column_name from all_tab_cols where owner='ME' and table_name='T1';
COLUMN_NAME
-----------
C1
SYS_C00002_10060107:25:40$
select column_name from all_tab_columns where owner='ME' and table_name='T1';
COLUMN_NAME
-----------
C1
答案 1 :(得分：1)
ALL_TAB_COLUMNS定义中唯一的过滤器是“where hidden_column ='NO'”，因此似乎UNUSED列在HIDDEN_COLUMN字段中被标记。
进一步研究数据定义视图，当列变为UNUSED时，看起来COL $ .PROPERTY设置为32800（位2 ^ 5和2 ^ 15）。 2 ^ 5用于标记隐藏的列，因此似乎2 ^ 15是UNUSED。您可以根据所需的内容创建ALL_TAB_COLS的自定义版本，例如：
CREATE OR REPLACE FORCE VIEW all_tab_cols_rev (owner,
table_name,
column_name,
data_type,
data_type_mod,
data_type_owner,
data_length,
data_precision,
data_scale,
nullable,
column_id,
default_length,
data_default,
num_distinct,
low_value,
high_value,
density,
num_nulls,
num_buckets,
last_analyzed,
sample_size,
character_set_name,
char_col_decl_length,
global_stats,
user_stats,
avg_col_len,
char_length,
char_used,
v80_fmt_image,
data_upgraded,
hidden_column,
virtual_column,
segment_column_id,
internal_column_id,
histogram,
qualified_col_name,
unused_column)
AS
SELECT u.NAME,
o.NAME,
c.NAME,
DECODE (c.type#,
1, DECODE (c.CHARSETFORM, 2, 'NVARCHAR2', 'VARCHAR2'),
2, DECODE (c.scale, NULL, DECODE (c.precision#, NULL, 'NUMBER', 'FLOAT'), 'NUMBER'),
8, 'LONG',
9, DECODE (c.CHARSETFORM, 2, 'NCHAR VARYING', 'VARCHAR'),
12, 'DATE',
23, 'RAW',
24, 'LONG RAW',
58, NVL2 (ac.synobj#, (SELECT o.NAME
FROM obj$ o
WHERE o.obj# = ac.synobj#), ot.NAME),
69, 'ROWID',
96, DECODE (c.CHARSETFORM, 2, 'NCHAR', 'CHAR'),
100, 'BINARY_FLOAT',
101, 'BINARY_DOUBLE',
105, 'MLSLABEL',
106, 'MLSLABEL',
111, NVL2 (ac.synobj#, (SELECT o.NAME
FROM obj$ o
WHERE o.obj# = ac.synobj#), ot.NAME),
112, DECODE (c.CHARSETFORM, 2, 'NCLOB', 'CLOB'),
113, 'BLOB',
114, 'BFILE',
115, 'CFILE',
121, NVL2 (ac.synobj#, (SELECT o.NAME
FROM obj$ o
WHERE o.obj# = ac.synobj#), ot.NAME),
122, NVL2 (ac.synobj#, (SELECT o.NAME
FROM obj$ o
WHERE o.obj# = ac.synobj#), ot.NAME),
123, NVL2 (ac.synobj#, (SELECT o.NAME
FROM obj$ o
WHERE o.obj# = ac.synobj#), ot.NAME),
178, 'TIME(' || c.scale || ')',
179, 'TIME(' || c.scale || ')' || ' WITH TIME ZONE',
180, 'TIMESTAMP(' || c.scale || ')',
181, 'TIMESTAMP(' || c.scale || ')' || ' WITH TIME ZONE',
231, 'TIMESTAMP(' || c.scale || ')' || ' WITH LOCAL TIME ZONE',
182, 'INTERVAL YEAR(' || c.precision# || ') TO MONTH',
183, 'INTERVAL DAY(' || c.precision# || ') TO SECOND(' || c.scale || ')',
208, 'UROWID',
'UNDEFINED'),
DECODE (c.type#, 111, 'REF'),
NVL2 (ac.synobj#, (SELECT u.NAME
FROM user$ u, obj$ o
WHERE o.owner# = u.user#
AND o.obj# = ac.synobj#), ut.NAME),
c.LENGTH,
c.precision#,
c.scale,
DECODE (SIGN (c.null$), -1, 'D', 0, 'Y', 'N'),
DECODE (c.col#, 0, TO_NUMBER (NULL), c.col#),
c.deflength,
c.default$,
h.distcnt,
h.lowval,
h.hival,
h.density,
h.null_cnt,
CASE
WHEN NVL (h.distcnt, 0) = 0
THEN h.distcnt
WHEN h.row_cnt = 0
THEN 1
WHEN ( h.bucket_cnt > 255
OR ( h.bucket_cnt > h.distcnt
AND h.row_cnt = h.distcnt
AND h.density * h.bucket_cnt <= 1) )
THEN h.row_cnt
ELSE h.bucket_cnt
END,
h.timestamp#,
h.sample_size,
DECODE (c.CHARSETFORM,
1, 'CHAR_CS',
2, 'NCHAR_CS',
3, NLS_CHARSET_NAME (c.CHARSETID),
4, 'ARG:' || c.CHARSETID),
DECODE (c.CHARSETID, 0, TO_NUMBER (NULL), NLS_CHARSET_DECL_LEN (c.LENGTH, c.CHARSETID) ),
DECODE (BITAND (h.spare2, 2), 2, 'YES', 'NO'),
DECODE (BITAND (h.spare2, 1), 1, 'YES', 'NO'),
h.avgcln,
c.spare3,
DECODE (c.type#,
1, DECODE (BITAND (c.property, 8388608), 0, 'B', 'C'),
96, DECODE (BITAND (c.property, 8388608), 0, 'B', 'C'),
NULL),
DECODE (BITAND (ac.flags, 128), 128, 'YES', 'NO'),
DECODE (o.status,
1, DECODE (BITAND (ac.flags, 256), 256, 'NO', 'YES'),
DECODE (BITAND (ac.flags, 2),
2, 'NO',
DECODE (BITAND (ac.flags, 4), 4, 'NO', DECODE (BITAND (ac.flags, 8), 8, 'NO', 'N/A') ) ) ),
DECODE (c.property, 0, 'NO', DECODE (BITAND (c.property, 32), 32, 'YES', 'NO') ),
DECODE (c.property, 0, 'NO', DECODE (BITAND (c.property, 8), 8, 'YES', 'NO') ),
DECODE (c.segcol#, 0, TO_NUMBER (NULL), c.segcol#),
c.intcol#,
CASE
WHEN NVL (h.row_cnt, 0) = 0
THEN 'NONE'
WHEN ( h.bucket_cnt > 255
OR ( h.bucket_cnt > h.distcnt
AND h.row_cnt = h.distcnt
AND h.density * h.bucket_cnt <= 1) )
THEN 'FREQUENCY'
ELSE 'HEIGHT BALANCED'
END,
DECODE (BITAND (c.property, 1024),
1024, (SELECT DECODE (BITAND (cl.property, 1), 1, rc.NAME, cl.NAME)
FROM SYS.col$ cl, attrcol$ rc
WHERE cl.intcol# = c.intcol# - 1
AND cl.obj# = c.obj#
AND c.obj# = rc.obj#(+)
AND cl.intcol# = rc.intcol#(+)),
DECODE (BITAND (c.property, 1), 0, c.NAME, (SELECT tc.NAME
FROM SYS.attrcol$ tc
WHERE c.obj# = tc.obj#
AND c.intcol# = tc.intcol#) ) ),
DECODE (c.property, 0, 'NO', DECODE (BITAND (c.property, 32768), 32768, 'YES', 'NO') )
FROM SYS.col$ c, SYS.obj$ o, SYS.hist_head$ h, SYS.user$ u, SYS.coltype$ ac, SYS.obj$ ot, SYS.user$ ut
WHERE o.obj# = c.obj#
AND o.owner# = u.user#
AND c.obj# = h.obj#(+)
AND c.intcol# = h.intcol#(+)
AND c.obj# = ac.obj#(+)
AND c.intcol# = ac.intcol#(+)
AND ac.toid = ot.oid$(+)
AND ot.type#(+) = 13
AND ot.owner# = ut.user#(+)
AND ( o.type# IN (3, 4) /* cluster, view */
OR ( o.type# = 2 /* tables, excluding iot - overflow and nested tables */
AND NOT EXISTS (
SELECT NULL
FROM SYS.tab$ t
WHERE t.obj# = o.obj#
AND ( BITAND (t.property, 512) = 512
OR BITAND (t.property, 8192) = 8192) ) ) )
AND ( o.owner# = USERENV ('SCHEMAID')
OR o.obj# IN (SELECT obj#
FROM SYS.objauth$
WHERE grantee# IN (SELECT kzsrorol
FROM x$kzsro) )
OR /* user has system privileges */
EXISTS (
SELECT NULL
FROM v$enabledprivs
WHERE priv_number IN
(-45 /* LOCK ANY TABLE */,
-47 /* SELECT ANY TABLE */,
-48 /* INSERT ANY TABLE */,
-49 /* UPDATE ANY TABLE */,
-50 /* DELETE ANY TABLE */) ) );
我将视图放在一个具有SELECT ANY DICTIONARY特权的单独锁定模式中，然后为它创建一个公共同义词。这样，您的所有用户都只能看到他们有权访问的表的UNUSED_COLUMN列。