Yep - oracle for example has hundreds of tables which hold metadata.
for example (this will look terrible due to the length of it but if you assume
it's 3 lines; a title line, some underlining for each column and the data
itself):
SQL> select * from all_tables where owner = 'FLYNNS' and table_name = 'QC11483';
OWNER TABLE_NAME TABLESPACE_NAME
CLUSTER_NAME IOT_NAME
STATUS PCT_FREE PCT_USED INI_TRANS MAX_TRANS INITIAL_EXTENT NEXT_EXTENT
MIN_EXTENTS MAX_EXTENTS PCT_INCREASE FREELISTS FREELIST_GROUPS LOGGING
BACKED_UP NUM_ROWS BLOCKS EMPTY_BLOCKS AVG_SPACE CHAIN_CNT AVG_ROW_LEN
AVG_SPACE_FREELIST_BLOCKS NUM_FREELIST_BLOCKS DEGREE INSTANCES CACHE
TABLE_LOCK SAMPLE_SIZE LAST_ANALYZED PARTITIONED IOT_TYPE TEMPORARY
SECONDARY NESTED BUFFER_POOL ROW_MOVEMENT GLOBAL_STATS USER_STATS DURATION
SKIP_CORRUPT MONITORING CLUSTER_OWNER DEPENDENCIES
COMPRESSION DROPPED
------------------------------ ------------------------------
------------------------------ ------------------------------
------------------------------ -------- ---------- ---------- ----------
---------- -------------- ----------- ----------- ----------- ------------
---------- --------------- ------- --------- ---------- ---------- ------------
---------- ---------- ----------- ------------------------- -------------------
---------- ---------- ----- ---------- ----------- ------------- -----------
------------ --------- --------- ------ ----------- ------------ ------------
---------- --------------- ------------ ----------
------------------------------ ------------ ----------- -------
FLYNNS QC11483 USERS
VALID 10 1 255 65536
1 2147483645 NO N
61517 1000 0 0 0 108
0 0 1 1 N ENABLED
61517 30/08/2017 16 NO N N NO
DEFAULT DISABLED YES NO DISABLED
YES DISABLED DISABLED NO
Executed in 0.141 seconds
There's something similar for SQL Server, DB2, ADDABAS, PostGres,, and so forth
S.
________________________________
From: Tutor <[email protected]> on behalf of
boB Stepp <[email protected]>
Sent: 14 October 2017 08:17
To: tutor
Subject: Re: [Tutor] How to test for the existence of a table in a sqlite3 db?
On Sat, Oct 14, 2017 at 2:11 AM, boB Stepp <[email protected]> wrote:
> So I get "None" as a result if the target table has not been created
> yet. But if I *do* create the table I want:
>
> py3: with open('create_sqlite3_db.sql') as f:
> ... sql = f.read()
> ...
> py3: c.executescript(sql)
> <sqlite3.Cursor object at 0x00000000026B4490>
> py3: tb_exists = "select name from sqlite_master where type='table'
> and name='BloodPressureReadings'"
> py3: tb_ck = c.execute(tb_exists).fetchone()
> py3: print(tb_ck)
> ('BloodPressureReadings',)
>
> So it is looking like I can use this technique to determine if I need
> to create the BloodPressureReadings table or not. Am I on track here
> or is there a better technique?
It just occurred to me after sending the above, does something like
"sqlite_master" exist for other database programs than sqlite3? Can I
abstract out "sqlite_master" and replace it with a variable so that I
can handle any kind of database?
--
boB
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