I have two tables: user, user_matching. And I wanna get items from both tables in 1 query. For example, SQL-like query:
select * from user where user.id = (select id from user_matching where id = user_matching_id)
Usually I should use 2 query in NoSQL DB. Now I do it like this:
Get from user_matching user_id
With user_id Get from user
Can I replace it with only 1 query using Tarantool. And How To?
You need to create stored procedure where you combine result of two selection, e.g.:
function select_user_by_matching_id(matching_id)
local id = box.space.user_matching:get{matching_id} # or :select
local user_data = box.space.user:get{id} # or :select
# work with user_data
return user_data
end
After you create this procedure you can call this procedure via Tarantool driver with fetching combined result.
More detail here: http://tarantool.org/doc/book/app/c-lua_tutorial.html?highlight=call
Related
I would like to do a big search on all field/columns names that contain "XYZ".
I tried below sql but it's giving me an error.
SELECT
table_name
,column_name
FROM information_schema.columns
WHERE column_name like '%account%'
order by table_name, column_name
ERROR states "Table or view not found: information_schema.columns; line 4, pos 5"
information_schema.columns is not supported in Databricks SQL. There are no in-built views available to get the complete details of tables along with columns. There is SHOW TABLES (database needs to be given) and SHOW COLUMNS (table name needs to be given).
You might have to use Pyspark capabilities to get the required result. First use the following code to get the details of all tables and respective columns:
db_tables = spark.sql(f"SHOW TABLES in default")
from pyspark.sql.functions import *
final_df = None
for row in db_tables.collect():
if(final_df is None):
final_df = spark.sql(f"DESCRIBE TABLE {row.database}.{row.tableName}")\
.withColumn('database',lit(f'{row.database}'))\
.withColumn('tablename',lit(f'{row.tableName}'))\
.select('database','tablename','col_name')
else:
final_df = final_df.union(spark.sql(f"DESCRIBE TABLE {row.database}.{row.tableName}")\
.withColumn('database',lit(f'{row.database}'))\
.withColumn('tablename',lit(f'{row.tableName}'))\
.select('database','tablename','col_name'))
#display(final_df)
final_df.createOrReplaceTempView('req')
Create a view and then apply the following query:
%sql
SELECT tablename,col_name FROM req WHERE col_name like '%id%' order by tablename, col_name
Currently, I'm working with Postgraphile and I need to enforce permissions at data/field level.
For example, I have a carmodel table, with my query is something like:
{
carmodel
{
id
name
description
}
}
Well, in this table I have ids (1 = AUDI, 2 = GM, 3 = BMW)
The current user (on roles/claims) has permission only to see (1=AUDI/3=BMW)
There is a way to enforce permissions based on field data? And return only data filtered on the user permissions?
Yes; row-level security can define this declaratively. Something like:
create policy audi_bmw on carmodel for select using (
id in (1, 3)
);
I'm guessing this permission comes from another table though; so it might be more like:
create policy audi_bmw on carmodel for select using (
id in (
select car_model_id
from user_carmodel_permissions
where user_id = current_user_id()
)
);
assuming you already have a current_user_id function, something like:
create function current_user_id() returns int as $$
select nullif(current_setting('jwt.claims.user_id', true), '')::int;
$$ language sql stable;
Check out our row level security cheatsheet.
$articles = Article::paginate(10, ['*'], 'pag');
What does the second parameter [*] above do?
The first parameters is the number of resources to be displayed by page.
The third parameter is the name of the query that will appear in the URL (i.e, "pag?=3").
What about "[*]"? I've used it for a long time without knowing what it does.
Don't tell me to search in Laravel Docs because I already did this and didn't find anything useful.
2nd parameter is select() method from Illuminate\Database\Eloquent\Builder which means select * from table ... limit 15.
You can specify which columns you want select from database.
For exaple $users->paginate(10, ['id', 'name']); -> select id, name from users ... limit 10
FYI: ['*'] is not fully qualified!
If you are using join in your select, it might be a problem if the columns with the same name are present in both tables. For example uuid, etc ...
In this case you should specify table name in select: ['table_name.*'] -> select table_name.* from table_name ... limit 15
Following is my query
$user = User::select(['uuid','name','about'])->with(['education','work'])->first();
this returns empty data for relationship education and work,
but if I remove select function from query I am getting data in relationship and it also returns all columns of user table which I don't want.
how can solve this problem
The problem is that relationships (with(...)) execute an additional query to get the related results. Let's say you have one to many relationship where users have many works. User::with('work')->find(1) will then execute these 2 queries:
select user where id = 1 and select works where user_id = 1.
So basically in order to be able to execute the second query (fetch relationship data) you need to include id (or whichever column you're referencing) in you select statement.
Fix:
$user = User::select(['uuid','name','about', 'id'])->with(['education','work'])->first();
Same principle in different forms applies to all relationships. For example in the inverse of hasMany which is belongsTo you would need to select the foreign key (for example user_id).
I have user with name, location, created_at as important fields in table.
I want to retrieve for each user the latest location,i.e, I want something like this:
username location created_at
abc New York 2012-08-18 16:18:57
xyz Mexico city 2012-08-18 16:18:57
abc Atlanta 2012-08-11 16:18:57
only input is UId(1,2) array of userids.please help me to accomplish this.I just want to know how to write query using active record query interface.
Generally, this should be a standard way to solve this kind of problems:
SELECT l1.user, l1.location
FROM locations l1
LEFT JOIN locations l2 ON l1.user = l2.user AND l2.created_at > l1.created_at
WHERE l2.id IS NULL
The idea is to join the table with itself, and find those rows which don't have any row with the same user and greater created_at.
Of course, you should have (user, created_at) index on your table.
Now you should see how would that be represented in AR interface.
When
u_id
is the array of user ids, then
u_id.map{|i| User.find(i).location}
should be an array of the users locations.
You can Use
User.where(:uid => [1,2,3]).maximum('location')
which will create something like
SELECT MAX(`users`.`location`) AS max_id FROM `users` WHERE `users`.`id` IN (1, 2,3)