No database selected. MySQL Query Browser - mysql

I am using MySQL Query Browser 1.2.17. My problem is that using EXACTLY the same query sometimes I get No database selected error.
I tried to find any dependence in using USE database; or FROM database.table.
I have no idea when will I get an error and when I won't and if I get I don't know how to solve this (since there is in the query USE database;).
UPDATE AND SOLUTION:
Since the problem was independent neither on the USE database; nor FROM database.table and has been observed RANDOMLY (ex. run query, it works, then immediately run again with the same query and it didn't work anymore), I recreated the database simply filling it with data from backup and it helped.

Best practice to write query.
databasename.tablename
example
SELECT * FROM database.table where 1 = 1

Related

SELECT MySQL using Sql Developer

I managed to connect to MySQL DB via Sql Developer following this guide. MySQL DB shows and I can expolre tables via the navigator. However, I could not run SELECT statement to show any of these tables. In MySQL workbench I used to use :
use [database_name]
Then, run select statement in that database. But in Sql developer, I am not sure what should I add to the statement to make it work. I have tried the following:
select *
from [table_name].[database_name];
It does not work. I found this tutorial, but nothing is mentioned about simple select statement. Any help is deeply appreciated.
AFAIK, except MySQL specific commands; all other standard SQL commands like SELECT,INSERT,UPDATE,DELETE should work just fine using SQL Developer. but per your posted query, it looks total strange.
Your query
select * from [table_name]#[database_name];
remove that # sign.
you should qualify like database_name.table_name.
Unless it's a typo, remove those [] as well from your query
statement.
Your query should look like
select * from database_name.table_name;
You can always write your SQL including database as well, in the form of:
database.tablename
such as:
select * from wordpressdb.usertable where username="someone"

How to use local DB table in a pass-through query?

I am currently working on a query in Access 2010 and I am trying to get the below query to work. I have the connection string between my local DB and the server that I am passing through to working just fine.
Select column1
, column2
from serverDB.dbo.table1
where column1 in (Select column1 from tbl_Name1)
In this situation table1 is the table on the server that I am passing through to get to, but the tbl_Name1 is the table that is actually in my Access DB that I am trying to use to create constraints on the data that I am pulling from the server.
When I try to run the query, I am getting the error that it doesn't think tbl_Name1 exists.
Any help is appreciated!
I just came across a solution that may help others in a similar situation.
This approach is easy because you can just run one query on your local Access database and get everything you need all at once. However, a lot of filtering/churning-through-results may be done on your own local computer behind the scenes, as opposed to on the remote server, so it may not necessarily be quick.
Steps
Create a query, make it a "Pass Through" query, and set up its "ODBC Connect Str" property to connect to the remote database.
Write the pass through query, something like SELECT RemoteId From RemoteTable and give your pass through query a name, maybe PassThroughQuery
Create a new query, make it a regular "Select" query.
Write your new query, using the pass through query you just created as a table in this new query (seems weird to use a query as a table, but it works) and join that PassThroughQuery "table" to your local table and filter it based on values in the local table, something like SELECT R.RemoteId, L.LocalValue FROM PassThroughQuery R INNER JOIN LocalTable L ON L.LocalId = R.RemoteId where L.LocalValue = 'SomeText'
This approach allows you to mix/join the results of a pass through query and the data in a local Access database table cleanly, albeit potentially slowly if there is a lot of data involved.
I think the issue is that a pass through query is one that is run on the server. Since one of the tables is located on the local Access file, it won't find the table.
Possible workaround if you must stay with the pass-through is you can build an SQL string with the results of the nested query rather than the query string itself (depending on the number of results this may or may not be practical)
e.g. Instead of Select column1 from tbl_Name1 you use "c1result1","c1result2",....

What is the size limit for a Query/View table in MySQL?

I am using MySQL and currently have 3 tables in a database. I created a view table with relationships between the 3 tables. The view table should be about 200 000 rows of data because i also tested the same query in Access and it works fine, but unfortunately i am not allowed to use Access.
When i build the view in MySQL i get a message that says the view was build successfully. But when i try to actually view the data, it gives me something like, MySQL ran out of memory. I am not sure what i can do differently to avoid this message. Can someone please give some advice?
You can use the Quick option for running your query.
Do not cache each query result, print each row as it is received. This
may slow down the server if the output is suspended. With this option,
mysql does not use the history file.

Conditional/Executable Comments in MySQL/SQL Server

Before I begin, I realize that what I'm attempting is bizarre and hackish. It's just for an isolated pen test, specifically SQL Injection.
What I need to do is write a SQL statement that behaves differently when executing on a MySQL database than it does when executing on a SQL Server Database.
Edit
The limitation of the Query I can build is that I can only change what's after the "WHERE id =" clause. I can't affect any other part of the query. Specifically, I need to be able to attach a " UNION SELECT * FROM some_other_table" that only gets executed by the SQL server to the end of my input.
This obviously would blow up MySQL because it doesn't have the tables I'm unioning.
Specifically:
SELECT * FROM USERS
WHERE id = My input -> (MySQL code: 'x' or 1=1 )
(MSSQL code 'x' or 1=1 UNION SELECT * FROM table)
The problem is, if either statement gets executed by the database it wasn't meant for, it blows up (and not in the way I need it to).
This lead to my discovery of Conditional/Executable Comments in MySQL.
SELECT * FROM USERS
WHERE id = /*! This will be executed but only by mysql */
That's great but I still can't prevent MySQL from executing MSSQL! I can only stop MSSQL from executing MySQL code.
My initial idea was to have a comment inside the MySQL conditional like:
SELECT * FROM USERS
WHERE id = /*! 4 or 1=1 --*/ MSSQL code that is ignored by mysql
But this throws an error saying to check my syntax at a line with nothing on it near ''.
I don't fully understand why this doesn't work but I know doesn't work with any form of MySQL comment I know of (Tried #, /*).
Is there a way to get my strange SQL statement to work? Or is there a way to do a conditional comment in MSSQL? I really just need MySQL to ignore anything after it's conditional but I have no idea how to make that happen without comments.
I'm not sure if this is what you need, but if I understand correctly you want one SQL statement that returns different results on MySQL vs. SQL Server (if that's what "behaves differently" means?). If so, one place to start would be using a system function that has the same name and syntax but different behaviour, such as SUBSTRING():
select substring('test', -1, 1)
On SQL Server that returns an empty string, but on MySQL it returns t. I don't know if using SUBSTRING() is viable in your case, but if not you may be able to find another function that's easier to use in your query.
If this doesn't help at all then I suggest you provide some more details about what limitations you have in building your query.

DatabaseLookup hangs on specific values

I use Kettle for some transformations and ran into a problem:
For one specific row, my DatabaseLookup step hangs. It just doesn't give a result. Trying to stop the transformation results in a never ending "Halting" for the lookup step.
The value given is nothing complicated at all, neither it is different from all other rows/values. It just won't continue.
Doing the same query in the database directly or in a different database tool (e.g. SQuirreL), it works.
I use Kettle/Spoon 4.1, the database is MySQL 5.5.10. It happens with Connector/J 5.1.14 and the one bundled with spoon.
The step initializes flawlessly (it even works for other rows) and I have no idea why it fails. No error message in the Spoon logs, nothing on the console/shell.
weird. Whats the table type? is it myisam? Does your transform also perform updates to the same table? maybe you are locking the table inadvertantly at the same time somehow?
Or maybe it's a mysql 5.5 thing.. But ive used this step extensively with mysql 5.0 and pdi 4.everything and it's always been fine... maybe post the transform?
I just found the culprit:
The lookup takes as a result the id field and gave it a new name, PERSON_ID. This FAILS in some cases! The resulting lookup/prepared statement was something like
select id as PERSON_ID FROM table WHERE ...
SOLUTION:
Don't use underscore in the "New name" for the field! With a new name of PERSONID everything works flawlessly for ALL rows!
Stupid error ...