I'm trying to retrieve the columns for PK from system tables and looking through the documentation I cannot see how I can get that information. SYS.SYSCONSTRAINTS does not contain column information.
I want to know which column belong to for the primary key. I find the tables in sys schema then I can get all the primary key info. The SQL is:
select t.tablename,
conglomeratename backIdxName,
cst.constraintname,
cst.type
from sys.systables t,
sys.sysconstraints cst,
sys.sysconglomerates cgl,
sys.syskeys sk
where isindex = 'TRUE'
and cgl.tableid = t.tableid
and (sk.constraintid = cst.constraintid and cst.type = 'P' and
sk.conglomerateid = cgl.conglomerateid)
and t.tableid = cst.tableid
and t.tabletype = 'T'
all the primary key is query out, but I wanna know the relation between primary key and column. I don't know which the column belong to for the primary key. I find sys.syscolumns table but nothing useful.
anybody know it ?
thanks.
Related
CREATE TABLE Flight (
FlightNo int NOT NULL PRIMARY KEY,
FlightDate Date,
PlaneSerialNo int,
EmployeeID int,
RouteNo int,
CONSTRAINT FK_PlaneSerialNo FOREIGN KEY(PlaneSerialNo)
REFERENCES Plane(PlaneSerialNo),
CONSTRAINT FK_EmployeeID FOREIGN KEY(EmployeeID)
REFERENCES Employee(EmployeeID),
CONSTRAINT FK_RouteNo FOREIGN KEY(RouteNo)
REFERENCES Route(RouteNo)
);
trying to create a sort of database system using oracle where it tracks flights but it just says the name is already used but havent seen any similarities in constraints other than identifying FKs
Oracle doesn't rely much on similarities - it has found object with exactly the same name in its dictionary and - as you can't have two objects with the same name - it raised the error.
Query user_constraints (and then user_objects, if previous search didn't find anything).
If you want to find out which table it is, you might try
select owner, table_name from dba_constraints where constraint_name = '<some value from your create table command>';
I am trying to fetch soecific columns data from relational table but it is giving me null
$allConsignments = Consignment::query();
$allConsignments->select(['id','customer_reference'])->with('customers:name,id')->orderBy('id', 'desc')->limit(5000)->get();
When I don't use select() then it gives correct data .
like this
$allConsignments = Consignment::query();
$allConsignments->with('customers:name,id')->orderBy('id', 'desc')->limit(5000)->get()
it is working but I also need specific columns from Consignment Table. what could be the reason?
You can also do like this.
$allConsignments = Consignment::query();
$allConsignments::with('customers:name,id')->orderBy('id', 'desc')->limit(5000)->get(['id','customer_reference']);
Actually, I also need to select the foreign key column from the table on which relationship is based. for example in my case I have customer_id in consignment table so it should be like that
$allConsignments = Consignment::query();
$allConsignments->select('id','customer_reference','customer_id')->with('customers:name,id')->orderBy('id', 'desc')->limit(5000)->get();
I need to select customer_id as well
In laravel, I create a migration table named 'timelogs'. Assumed that, this table have three column id,userid,value. 'id' is primary key and have auto increment property , 'userid' is foreign key. I insert data 1,2,2,2,2 and 3,4,5,6,7 for'userid' and 'value' field respectively.
Now I want to find last inserted record.Such as userid = 2 and value = 7.Here userid field contain different user's id. I want to find specific user's last record. How can I do this without using primary key?
$last_record = DB::table('timelogs')->where('userid', $user_id)->orderBy('id', 'desc')->first();
//var_dump($last_record);
It's been a while since I've written code, and I never used SQLite before, but many-to-many relationships used to be so fundamental, there must be a way to make them fast...
This is a abstracted version of my database:
CREATE TABLE a (_id INTEGER PRIMARY KEY, a1 TEXT NOT NULL);
CREATE TABLE b (_id INTEGER PRIMARY KEY, fk INTEGER NOT NULL REFERENCES a(_id));
CREATE TABLE d (_id INTEGER PRIMARY KEY, d1 TEXT NOT NULL);
CREATE TABLE c (_id INTEGER PRIMARY KEY, fk INTEGER NOT NULL REFERENCES d(_id));
CREATE TABLE b2c (fk_b NOT NULL REFERENCES b(_id), fk_c NOT NULL REFERENCES c(_id), CONSTRAINT PK_b2c_desc PRIMARY KEY (fk_b, fk_c DESC), CONSTRAINT PK_b2c_asc UNIQUE (fk_b, fk_c ASC));
CREATE INDEX a_a1 on a(a1);
CREATE INDEX a_id_and_a1 on a(_id, a1);
CREATE INDEX b_fk on b(fk);
CREATE INDEX b_id_and_fk on b(_id, fk);
CREATE INDEX c_id_and_fk on c(_id, fk);
CREATE INDEX c_fk on c(fk);
CREATE INDEX d_id_and_d1 on d(_id, d1);
CREATE INDEX d_d1 on d(d1);
I have put in any index i could think of, just to make sure (and more than is reasonable, but not a problem, since the data is read only). And yet on this query
SELECT count(*)
FROM a, b, b2c, c, d
WHERE a.a1 = "A"
AND a._id = b.fk
AND b._id = b2c.fk_b
AND c._id = b2c.fk_c
AND d._id = c.fk
AND d.d1 ="D";
the relation table b2c does not use any indexes:
0|0|2|SCAN TABLE b2c
0|1|1|SEARCH TABLE b USING INTEGER PRIMARY KEY (rowid=?)
0|2|0|SEARCH TABLE a USING INTEGER PRIMARY KEY (rowid=?)
0|3|3|SEARCH TABLE c USING INTEGER PRIMARY KEY (rowid=?)
0|4|4|SEARCH TABLE d USING INTEGER PRIMARY KEY (rowid=?)
The query is about two orders of magnitude to slow to be usable. Is there any way to make SQLite use an index on b2c?
Thanks!
In a nested loop join, the outermost table does not use an index for the join (because the database just goes through all rows anyway).
To be able to use an index for a join, the index and the other column must have the same affinity, which usually means that both columns must have the same type.
Change the types of the b2c columns to INTEGER.
If the lookups on a1 or d1 are very selective, using a or d as the outermost table might make sense, and would then allow to use an index for the filter.
Try running ANALYZE.
If that does not help, you can force the join order with CROSS JOIN or INDEXED BY.
I have this table in cassandra
CREATE TABLE global_product_highlights (
deal_id text,
product_id text,
highlight_strength double,
category_id text,
creation_date timestamp,
rank int,
PRIMARY KEY (deal_id, product_id, highlight_strength)
)
When i fire below query in Golang
err = session.Query("select product_id from global_product_highlights where category_id=? order by highlight_strength DESC",default_category).Scan(&prodId_array)
I get ERROR : ORDER BY with 2ndary indexes is not supported.
I have an index on category_id.
I don't completely understand how is secondary index applied on composite keys in cassandra.
Appreciate if anyone would explain and rectify this one.
The ORDER BY clause in Cassandra only works on your first clustering column (2nd column in the primary key), which in this case is your product_id. This DataStax doc states that:
Querying compound primary keys and sorting results ORDER BY clauses
can select a single column only. That column has to be the second
column in a compound PRIMARY KEY.
So, if you want to have your table sorted by highlight_strength, then you'll need to make that field the first clustering column.