How do I get column datatype in Oracle with PL-SQL

问题:

I have "read only" access to a few tables in an Oracle database. I need to get schema information on some of the columns. I'd like to use something analogous to MS SQL's sp_help.

I see the table I'm interested in listed in this query:

SELECT * FROM ALL_TABLES

When I run this query, Oracle tells me "table not found in schema", and yes the parameters are correct.

SELECT 
DBMS_METADATA.GET_DDL('TABLE', 'ITEM_COMMIT_AGG', 'INTAMPS') AS DDL
FROM DUAL;

After using my Oracle universal translator 9000 I've surmised this doesn't work because I don't have sufficient privileges. Given my constraints how can I get the datatype and data length of a column on a table I have read access to with a PL-SQL statement?

回答1:

ALL_TAB_COLUMNS should be queryable from PL/SQL. DESC is a SQL*Plus command.

SQL> desc all_tab_columns;
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 OWNER                                     NOT NULL VARCHAR2(30)
 TABLE_NAME                                NOT NULL VARCHAR2(30)
 COLUMN_NAME                               NOT NULL VARCHAR2(30)
 DATA_TYPE                                          VARCHAR2(106)
 DATA_TYPE_MOD                                      VARCHAR2(3)
 DATA_TYPE_OWNER                                    VARCHAR2(30)
 DATA_LENGTH                               NOT NULL NUMBER
 DATA_PRECISION                                     NUMBER
 DATA_SCALE                                         NUMBER
 NULLABLE                                           VARCHAR2(1)
 COLUMN_ID                                          NUMBER
 DEFAULT_LENGTH                                     NUMBER
 DATA_DEFAULT                                       LONG
 NUM_DISTINCT                                       NUMBER
 LOW_VALUE                                          RAW(32)
 HIGH_VALUE                                         RAW(32)
 DENSITY                                            NUMBER
 NUM_NULLS                                          NUMBER
 NUM_BUCKETS                                        NUMBER
 LAST_ANALYZED                                      DATE
 SAMPLE_SIZE                                        NUMBER
 CHARACTER_SET_NAME                                 VARCHAR2(44)
 CHAR_COL_DECL_LENGTH                               NUMBER
 GLOBAL_STATS                                       VARCHAR2(3)
 USER_STATS                                         VARCHAR2(3)
 AVG_COL_LEN                                        NUMBER
 CHAR_LENGTH                                        NUMBER
 CHAR_USED                                          VARCHAR2(1)
 V80_FMT_IMAGE                                      VARCHAR2(3)
 DATA_UPGRADED                                      VARCHAR2(3)
 HISTOGRAM                                          VARCHAR2(15)

回答2:

You can use the desc command.

desc MY_TABLE

This will give you the column names, whether null is valid, and the datatype (and length if applicable)

回答3:

Note: if you are trying to get this information for tables that are in a different SCHEMA use the all_tab_columns view, we have this problem as our Applications use a different SCHEMA for security purposes.

use the following:

EG:

SELECT
    data_length 
FROM
    all_tab_columns 
WHERE
    upper(table_name) = 'MY_TABLE_NAME' AND upper(column_name) = 'MY_COL_NAME'

回答4:

The best solution that I've found for such case is

select column_name, data_type||
case
when data_precision is not null and nvl(data_scale,0)>0 then '('||data_precision||','||data_scale||')'
when data_precision is not null and nvl(data_scale,0)=0 then '('||data_precision||')'
when data_precision is null and data_scale is not null then '(*,'||data_scale||')'
when char_length>0 then '('||char_length|| case char_used 
                                                         when 'B' then ' Byte'
                                                         when 'C' then ' Char'
                                                         else null 
                                           end||')'
end||decode(nullable, 'N', ' NOT NULL')
from user_tab_columns
where table_name = 'TABLE_NAME'
and column_name = 'COLUMN_NAME';

@Aaron Stainback, thank you for correction!

回答5:

select t.data_type 
  from user_tab_columns t 
 where t.TABLE_NAME = 'xxx' 
   and t.COLUMN_NAME='aaa'

回答6:

Oracle: Get a list of the full datatype in your table:

select data_type || '(' || data_length || ')' 
from user_tab_columns where TABLE_NAME = 'YourTableName'

回答7:

select column_name, data_type || '(' || data_length || ')' as datatype
from all_tab_columns 
where TABLE_NAME = upper('myTableName')

回答8:

Quick and dirty way (e.g. to see how data is stored in oracle)

SQL> select dump(dummy) dump_dummy, dummy
     , dump(10) dump_ten
from dual

DUMP_DUMMY       DUMMY DUMP_TEN            
---------------- ----- --------------------
Typ=1 Len=1: 88  X     Typ=2 Len=2: 193,11 
1 row selected.

will show that dummy column in table sys.dual has typ=1 (varchar2), while 10 is Typ=2 (number).