I want to verify if an index exists for a SQL table. I'm trying this command (from here) :
SELECT *
FROM sys.indexes
WHERE name='YourIndexName' AND object_id = OBJECT_ID('Schema.YourTableName')
But I'm getting the error :
OperationalError: no such table: sys.indexes
with sqlite3 in Python.
SELECT
*
FROM
sqlite_master
WHERE
type= 'index' and tbl_name = 'your_table_name' and name = 'your_index_name';
You can use above query to verify index exist for a specific table and specific name.
Related
sqlite> create table t
...> SELECT * FROM sqlite_master WHERE type='table' AND name='t';
Error: near "SELECT": syntax error
sqlite>
I'm trying to create a table called 't' in terminal. I'm getting the error. Maybe I'm missing somewhere?
The syntax you need to use here is CREATE TABLE AS ... SELECT:
> CREATE TABLE t AS SELECT * FROM sqlite_master WHERE type = 'table' AND name = 't';
I have 2 tables with identical structure I want to update one table using data from the other, matching on primary key. SQLite has a with (CTE) statement but the following doesn't work (sqlite3 v. 3.29.0):
sqlite> select * from main;
1|A
2|B
4|D
5|E
6|F
sqlite> select * from temp;
1|aa
2|bb
3|cc
4|dd
5|ee
sqlite> with mapping as (select main.ID, temp.Desc from main join temp on temp.ID=main.ID) update main set Desc=mapping.Desc where main.ID=mapping.ID;
Error: no such column: mapping.Desc
I've tried using "select main.ID as ID, temp.Desc as Desc", but get the same error message.
To update your main table from your cte, use a subquery, since sqlite doesn't support update from
with mapping as
(select main.ID, temp.Desc
from main
join temp on temp.ID=main.ID)
update main set Desc=
(select Desc from mapping where ID = main.ID limit 1);
see dbfiddle
This works:
sqlite> .databases
seq name file
--- --------------- ----------------------------------------------------------
0 main /path/to/db
2 uni /path/to/db
also this:
sqlite> pragma main.table_info(tsv_storage);
0|id|int|0||0
1|seqid|text|0||0
...
and this:
sqlite> select count(*) from main.tsv_storage;
198159
and also the attached database works:
sqlite> select * from uni.fasta_storage where uni.fasta_storage.id = 1;
1 MASNTVSAQ... Q197F8.1 002R_IIV3 Uncharacterized protein 002R Q197F8
but this not:
sqlite> select main.tsv_storage.seqid where main.tsv_storage.id=8;
Error: no such column: main.tsv_storage.seqid
EDIT:
and I have also problems with this, do I have to join the tables?
insert into main.tsv_storage(seqlength) select length(fasta) from
uni.fasta_storage where uni.fasta_storage.title = main.tsv_storage.seqid;
Error: no such column: main.tsv_storage.seqid
It happens for all columns, not only seqid. I think I did everything that is explained here: http://sqlite.awardspace.info/syntax/sqlitepg12.htm
What am I missing?
sqlite> select * from main.tsv_storage.seqid where main.tsv_storage.id=8;
You have not defined where to look for the selection. You need to tell the query what fields to search within the table, then define which table you are searching. The select * portion tells the query to look in all fields within the table. The from portion of the query tells the processes what table to look in. And lastly the where portion tells the query what to match when looking.
When using INSERT ... SELECT ..., the SELECT part must be valid query.
You cannot access a column like main.tsv_storage without having the table in the FROM clause:
INSERT INTO main.tsv_storage(seqlength)
SELECT length(fasta)
FROM uni.fasta_storage, main.tsv_storage
WHERE uni.fasta_storage.title = main.tsv_storage.seqid;
And the entire commands looks suspicious.
Are you sure you don't want to update the values in the seqlength column for existing records?
In that case, you would use something like this:
UPDATE main.tsv_storage
SET seqlength = (SELECT length(fasta)
FROM uni.fasta_storage
WHERE uni.fasta_storage.title = main.tsv_storage.seqid);
Is there a way of listing ALL foreign keys in a SQLite database?
They don't seem to be stored in sqlite_master and PRAGMA foreign_key_list('table') only lists one at a time.
Alternatively, is there a way of listing what foreign keys reference a table?
It seems that all (or many) of the PRAGMA commands can be programatically selected with a little trick;
Usually the are called like:
PRAGMA table_info('my_table');
PRAGMA foreign_key_list('my_table');
But this can also be done:
SELECT * FROM pragma_table_info('my_table');
SELECT * FROM pragma_foreign_key_list('my_table');
And the schema can also be (more or less) obtained:
.schema pragma_table_info
/* pragma_table_info(cid,name,type,"notnull",dflt_value,pk) */;
.schema pragma_foreign_key_list
/* pragma_foreign_key_list(id,seq,"table","from","to",on_update,on_delete,"match") */
So, to get all the fks a JOIN between sqlite_master and pragma_foreign_key_list can do the trick:
SELECT
m.name
, p.*
FROM
sqlite_master m
JOIN pragma_foreign_key_list(m.name) p ON m.name != p."table"
WHERE m.type = 'table'
ORDER BY m.name
;
Just take care, that some fields of pragma_foreign_key_list like table, from, ... must be quoted;
With the SQLite shell, use the .schema instruction, and use GREP to filter lines containing REFERENCES.
From shell.c in the SQLite repository, today's version in the trunk, two queries:
SELECT sql
FROM (
SELECT sql sql, type type, tbl_name tbl_name, name name
FROM sqlite_master
UNION ALL
SELECT sql, type, tbl_name, name
FROM sqlite_temp_master
)
WHERE tbl_name LIKE shellstatic()
AND type != 'meta'
AND sql NOTNULL
ORDER BY substr(type, 2, 1), name
and
SELECT sql
FROM (
SELECT sql sql, type type, tbl_name tbl_name, name name
FROM sqlite_master
UNION ALL
SELECT sql, type, tbl_name, name
FROM sqlite_temp_master
)
WHERE type != 'meta'
AND sql NOTNULL
AND name NOT LIKE 'sqlite_%'
ORDER BY substr(type, 2, 1), name
The second one is probably what you are looking for.
How can I get the list of all the available tables in sqlite programmatically?
try this :
SELECT * FROM sqlite_master where type='table';
Use the below sql statement to get list of all table in sqllite data base
SELECT * FROM dbname.sqlite_master WHERE type='table';
The same question asked before on StackOverFlow.
How to list the tables in an SQLite database file that was opened with ATTACH?
worked for me
SELECT * FROM sqlite_master where type='table'
con = sqlite3.connect('db.sqlite')
cur = con.cursor()
cur.execute('''
SELECT tbl_name
FROM sqlite_master
WHERE type = 'table';
''')
print(cur.fetchall())