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MySQL select several columns of several tables at the same time without using JOIN


MySQL select several columns of several tables at the same time without using JOIN

By : akafred
Date : November 22 2020, 10:40 AM
I wish did fix the issue. I don't want to use JOIN because I have read it will decrease the perfomance`
What did you find when you measured it?
code :
#1241 - Operand should contain 1 column(s)
(SELECT field_id, url FROM
#1242 - Subquery returns more than 1 row


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Select All columns for all tables in join + linq join

Select All columns for all tables in join + linq join


By : user1543964
Date : March 29 2020, 07:55 AM
around this issue While you cant expand them to columns, you can simply return the entities. Eg:
code :
select new { CTLJCRJOB, CTLRFDSTM }
php mysql select from columns from 2 tables Join

php mysql select from columns from 2 tables Join


By : Sourabh Maheshwari
Date : March 29 2020, 07:55 AM
I hope this helps you . I have two tables. visitors_details, with id,scanner_id,time columns and visitors_info with scanner_id, name,surname columns , Its better to enable some debugging for your code like this:
code :
<?php
error_reporting(E_ALL);
$sql = "
SELECT d.id AS id, i.name AS name, i.surname AS surname, d.time  AS time 
  FROM visitors_details AS d 
  LEFT JOIN visitors_info AS i ON d.scanner_id=i.scanner_id
";

$result = mysql_query($sql);
if (!$result) {
    die('Invalid query: ' . mysql_error());
}

?> 
How do I join two tables and then select two different columns?

How do I join two tables and then select two different columns?


By : David Strootman
Date : March 29 2020, 07:55 AM
I think the issue was by ths following , I searched and tried to find a solution for this for a week now, but I'm stuck. I am trying to select two different columns in one table and comparing them with another database. This is my setup:
code :
select 
  m.match_id, 
  f1.fightr_namn as fighter1Name, 
  f2.fightr_namn as fighter2Name 
from matches m
inner join fighters f1 on m.fightr_id1 = f1.fightr_id
inner join fighters f2 on m.fightr_id2 = f2.fightr_id
MySQL - Left Join, Select all columns left, few columns on the right tables,

MySQL - Left Join, Select all columns left, few columns on the right tables,


By : W1nd
Date : March 29 2020, 07:55 AM
like below fixes the issue I'm trying to join two tables together as shown below, in the " * " section, I'm having trouble doing the following, , Yes, add the table name before the * to select all columns of a table
code :
SELECT nutrients.*, measures.colX
FROM nutrients 
LEFT JOIN measures ON nutrients.name=measures.name
mysql select from 3 tables where not all tables contain infos in the same amount of rows (Inner Join?!)

mysql select from 3 tables where not all tables contain infos in the same amount of rows (Inner Join?!)


By : Edgar Garcia
Date : March 29 2020, 07:55 AM
help you fix your problem When starting to write a query think about what data you want to show. In your case you want to show data from table1 and table3, so join these and select from them. The criteria on table2 belong in the WHERE clause.
The criteria on table2 are:
code :
select t1.id, t1.name, t3.description
from t1
join t3 on t3.item_id = t1.item_id
where t1.active = 1
and 
(
  not exists
  (
    select *
    from t2
    where t2.item_id = t1.item_id
  )
  or
  exists
  (
    select *
    from t2
    where t2.item_id = t1.item_id
    and (instock > 0 or deliverytimes != 'sold')
  )
);
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