I'm using MySQL and have a table of 9 million rows and would like to quickly check if a record (id) exists or not.
Based on some research it seems the fastest way is the following sql:
SELECT EXISTS(SELECT 1 FROM table1 WHERE id = 100)
Source: Best way to test if a row exists in a MySQL table
How can I write this using Laravel's query builder?
Use selectOne method of the Connection class:
$resultObj = DB::selectOne('select exists(select 1 from your_table where id=some_id) as `exists`');
$resultObj->exists; // 0 / 1;
see here http://laravel.com/docs/4.2/queries
Scroll down to Exists Statements, you will get what you need
DB::table('users')
->whereExists(function($query)
{
$query->select(DB::raw(1))
->from('table1')
->whereRaw("id = '100'");
})
->get();
This is an old question that was already answered, but I'll post my opinion - maybe it'll help someone down the road.
As mysql documentation suggests, EXISTS will still execute provided subquery. Using EXISTS is helpful when you need to have it as a part of a bigger query. But if you just want to check from your Laravel app if record exists, Eloquent provides simpler way to do this:
DB::table('table_name')->where('field_name', 'value')->exists();
this will execute query like
select count(*) as aggregate from `table_name` where `field_name` = 'value' limit 1
// this is kinda the same as your subquery for EXISTS
and will evaluate the result and return a true/false depending if record exists.
For me this way is also cleaner then the accepted answer, because it's not using raw queries.
Update
In laravel 5 the same statement will now execute
select exists(select * from `table_name` where `field_name` = 'value')
Which is exactly, what was asked for.
Related
The table in question has ~30mio records. Using Entity Framework I write a LINQ Query like this:
dbContext.MyTable.FirstOrDefault(t => t.Col3 == "BQJCRHHNABKAKU-KBQPJGBKSA-N");
Devart DotConnect for Oracle generates this:
SELECT
Extent1.COL1,
Extent1.COL2,
Extent1.COL3
FROM MY_TABLE Extent1
WHERE (Extent1.COL3 = :p__linq__0) OR ((Extent1.COL3 IS NULL) AND (:p__linq__0 IS NULL))
FETCH FIRST 1 ROWS ONLY
The query takes about four minutes, obviously a full table scan.
However, handcrafting this SQL:
SELECT
Extent1.COL1,
Extent1.COL2,
Extent1.COL3
FROM MY_TABLE Extent1
WHERE Extent1.COL3 = :p__linq__0
FETCH FIRST 1 ROWS ONLY
returns the expected match in 200ms.
Question: Why is it so? I would expect the query optimizer to note that the right part is false if the parameter is not null, so why doesn't the first query hit the index?
Please set UseCSharpNullComparisonBehavior=false explicitly:
var config = Devart.Data.Oracle.Entity.Configuration.OracleEntityProviderConfig.Instance;
config.QueryOptions.UseCSharpNullComparisonBehavior = false;
If this doesn't help, send us a small test project with the corresponding DDL script so that we can investigate the issue.
Is there ability to make a multiple update with subquery on Symfony3 with Doctrine query builder or DQL?
For example, I want to run this query:
UPDATE tableA
SET fieldA2 = max_field2
FROM (SELECT
field1,
max(field2) AS max_field2
FROM table
GROUP BY field1) AS subquery
WHERE subquery.field1 = tableA.field1;
I can't understand how to use $entityManager->createQuery()->update with FROM subquery.
As far as I know, it's not possible through DQL.
You need to go through a loop.
foreach($entities as entity)
{
$em->flush();
}
Else, you will consider Batch processing, or just use plain SQL. So it might be usefull to check DBAL.
I need to update a column in one table with the results from a select sub-query (and they should ultimately be different). But When I do this, I get the 'ORA-01427: single row sub-query returns more than one row query' error.
Can you please take a look and see what it is that I am overlooking? (I could just be overlooking something simple for all I know)
UPDATE AIRMODEL_NETWORK_SUMMARY ans
SET ANS.NBR_RETURNS = (
SELECT SUM(RQ.RETURN_QTY)
FROM RETURN_QTY RQ JOIN AIRMODEL_NETWORK_SUMMARY ANS ON RQ.LOC_ID = ANS.LOC_ID
WHERE RQ.FSCL_YR_NUM = ans.FSCL_YR_NUM
AND RQ.FSCL_WK_IN_YR_NUM =
ans.FSCL_WK_IN_YR_NUM
GROUP BY ANS.LOC_ID,
ans.FSCL_WK_IN_YR_NUM,
ANS.FSCL_YR_NUM
);
I think that your inner query is not well correlated to the table that you're trying to update. Please look here Oracle SQL: Update a table with data from another table. You should add some kind of a where condition that ties the rows you're trying to update with the values calculated by the inner statement.
I have created a view in oracle. Now i would like to fetch data from that view. So i have written a SQL Query. But the query is not working for not having a specific condition. But if I give that condition the query executes. But the problem is not occurring if i joined the same number of tables (that were used to create view) instead of using view. In the following I am giving the oracle query.
SELECT *
FROM "920_search_report"
WHERE lm_culture = '7aacb509-271d-4aca-e040-e00adea40aae'
AND hand_person_info_guid = 'eebd4257-7856-4c6e-b6b8-9b886e89e397'
AND ( Lower(handicap_type) LIKE Lower('%DQ871J%')
OR Lower(skskodenr) LIKE Lower('%DQ871J%') );
The above query executes and returns one record but if I omit or comment the third line then the query does not return any records, but it should return one or two. the query is given below:
SELECT *
FROM "920_search_report"
WHERE lm_culture = '7aacb509-271d-4aca-e040-e00adea40aae'
--AND HAND_PERSON_INFO_GUID='eebd4257-7856-4c6e-b6b8-9b886e89e397'
AND ( Lower(handicap_type) LIKE Lower('%DQ871J%')
OR Lower(skskodenr) LIKE Lower('%DQ871J%') );
Can anyone help me to solve the problem.
How do I select multiple rows from SQL?
ie. $results->row(1,2,3,4,5,10)
Are you using ActiveRecord? If so, you can use the where_in() method when making your query. It's not something you do after the query is finished, as you seem to be doing in your example.
$this->db->where_in('id', array(1,2,3,4,5,10));
$query = $this->db->get('myTable');
// This produces the query SELECT * FROM `myTable` WHERE `id` IN (1,2,3,4,5,10)
See the this CodeIgniter docs section for more info on SELECT statement support.