I have a SQL Server database and having a table containing too many records. Before it was working fine but now when I run SQL Statement takes time to execute.
Sometime cause the SQL Database to use too much CPU.
This is the Query for the table.
CREATE TABLE [dbo].[tblPAnswer1](
[ID] [bigint] IDENTITY(1,1) NOT NULL,
[AttrID] [int] NULL,
[Kidato] [int] NULL,
[Wav] [int] NULL,
[Was] [int] NULL,
[ShuleID] [int] NULL,
[Mwaka] [int] NULL,
[Swali] [float] NULL,
[Wilaya] [int] NULL,
CONSTRAINT [PK_tblPAnswer1] PRIMARY KEY CLUSTERED
(
[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
And the following down is the sql stored procedure for the statement.
ALTER PROC [dbo].[uspGetPAnswer1](#ShuleID int, #Mwaka int, #Swali float, #Wilaya int)
as
SELECT ID,
AttrID,
Kidato,
Wav,
Was,
ShuleID,
Mwaka,
Swali,
Wilaya
FROM dbo.tblPAnswer1
WHERE [ShuleID] = #ShuleID
AND [Mwaka] = #Mwaka
AND [Swali] = #Swali
AND Wilaya = #Wilaya
What is wrong in my SQL Statement. Need help.
Just add an index on ShuleID, Mwaka, Swali and Wilaya columns. The order of columns in the index should depend on distribution of data (the columns with most diverse values in it should be the first in the index, and so on).
And if you need it super-fast, also include all the remaining columns used in the query, to have a covering index for this particular query.
EDIT: Probably should move the float col (Swali) from indexed to included columns.
Add an Index on the ID column and include ShuleID, Mwaka, Swali and Wilaya columns. That should help improve the speed of the query.
CREATE NONCLUSTERED INDEX IX_ID_ShuleID_Mwaka_Swali_Wilaya
ON tblPAnswer1 (ID)
INCLUDE (ShuleID, Mwaka, Swali, Wilaya);
What is the size of the table? You may need additional indices as you are not using the primary key to query the data. This article by Pinal Dave provides a script to identify missing indices.
http://blog.sqlauthority.com/2011/01/03/sql-server-2008-missing-index-script-download/
It provides a good starting point for index optimization.
Related
i have the following table structure :
CREATE TABLE [dbo].[TableABC](
[Id] [bigint] IDENTITY(1,1) NOT NULL,
[FieldA] [nvarchar](36) NULL,
[FieldB] [int] NULL,
[FieldC] [datetime] NULL,
[FieldD] [nvarchar](255) NULL,
[FieldE] [decimal](19, 5) NULL,
PRIMARY KEY CLUSTERED
(
[Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
I do two type of CRUD operations with this table.
SELECT * FROM [dbo].[TableABC] WHERE FieldA = #FieldA
INSERT INTO [dbo].[TableABC](FieldA,FieldB,FieldC,FieldD,FieldE) VALUES (#FieldA,#FieldB,#FieldC,#FieldD,#FieldE)
FieldA has a unique value, but there is no constraint in the table.
Currently there are 6070755 rows in the table. Along with data growing , performance is getting slow.
Any suggestion , how to improve perfomance ? How to make CREATE and READ operation faster ?
now i faced problem , that select and insert takes too long , sometime more then 60 seconds
Read up on SQL basics- and Indices DEFINITELY are one. And if you have a unique value and no index on the field (constraint is irrelevant, unique index is good neough) - yes, that will get slower. SQL Server has to check the whole table.
So:
Add a unique index to Field a.
Given your 2 statements and the little "FieldA has a unique value, but there is no constraint in the table." I assume you are trying to enforce unique values there by selecting first. This will slow you down.
Instead make the index, and then try/catch the non unique sql errors - WAY faster. WAY faster. The index will make the insert a LITTLE slower, but you can save on the very slow select you do not totally.
Using version:
Microsoft SQL Server 2008 R2 (SP3-OD) (KB3144114) - 10.50.6542.0 (Intel X86)
Feb 22 2016 18:12:09
Copyright (c) Microsoft Corporation
Standard Edition on Windows NT 5.2 <X86> (Build : )
I have a heavy table (135K rows), that I moved from another DB.
It transferred with the [id] column being a standard int column instead of it being the key & seed column.
When trying to edit that field to become an identity specification, with a seed value, its errors out and gives me this error:
Execution Timeout Expired.
The timeout period elapsed prior to completion of the operation...
I even tried deleting that column, to try recreate it later, but i get the same issue.
Thanks
UPDATE:
Table structure:
CREATE TABLE [dbo].[tblEmailsSent](
[id] [int] IDENTITY(1,1) NOT NULL, -- this is what it should be. currently its just an `[int] NOT NULL`
[Sent] [datetime] NULL,
[SentByUser] [nvarchar](50) NULL,
[ToEmail] [nvarchar](150) NULL,
[StudentID] [int] NULL,
[SubjectLine] [nvarchar](200) NULL,
[MessageContent] [nvarchar](max) NULL,
[ReadStatus] [bit] NULL,
[Folder] [nvarchar](50) NULL,
CONSTRAINT [PK_tblMessages] PRIMARY KEY CLUSTERED
(
[id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
GO
I think that your question is a duplicate of Adding an identity to an existing column. That question above has an answer that should be perfect for your situation. I'll reproduce its essential part here below.
But before that, let's clarify why you see the timeout error.
You are trying to add the IDENTITY property to existing column. And you are using SSMS GUI for it. A simple ALTER COLUMN statement can't do it and even if it could, SSMS generates a script that creates a new table, copies over the data into the new table, drops the old table and renames the new table to the old name. When you do this operation via SSMS GUI it runs its scripts with a predefined timeout of 30 seconds.
Of course, you can change this setting in SSMS and increase the timeout, but there is a much better way.
Simple/lazy way
Use SSMS GUI to change the column definition, but then instead of clicking "Save", click "Generate Change Script" in the table designer.
Then save this script to a file and review the generated T-SQL code that GUI runs behind the scene.
You'll see that it creates a temp table with the required schema, copies data over, re-creates foreign keys and indexes, drops the old table and renames the new table.
The script itself is usually correct, but pay close attention to transactions in it. For some reason SSMS often doesn't use a single transaction for the whole operation, but several transactions. I'd recommend to manually review the script and make sure that there is only one BEGIN TRANSACTION at the top and one COMMIT in the end. You don't want to end up with a half-done operation with, say, a table where all indexes and foreign keys were dropped.
If it is a one-off operation, it could be enough for you. Your table is only 2.4GB, so it may take few minutes, but it should not be hours.
If you run the T-SQL script yourself in SSMS, then by default there is no timeout. You can stop it yourself if it takes too long.
Smart and fast way to do it is described in details in this answer by Justin Grant.
The main idea is to use the ALTER TABLE...SWITCH statement to make the change only touching the metadata without touching each page of the table.
BEGIN TRANSACTION;
-- create a new table with required schema
CREATE TABLE [dbo].[NEW_tblEmailsSent](
[id] [int] IDENTITY(1,1) NOT NULL,
[Sent] [datetime] NULL,
[SentByUser] [nvarchar](50) NULL,
[ToEmail] [nvarchar](150) NULL,
[StudentID] [int] NULL,
[SubjectLine] [nvarchar](200) NULL,
[MessageContent] [nvarchar](max) NULL,
[ReadStatus] [bit] NULL,
[Folder] [nvarchar](50) NULL,
CONSTRAINT [PK_tblEmailsSent] PRIMARY KEY CLUSTERED
(
[id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
-- switch the tables
ALTER TABLE [dbo].[tblEmailsSent] SWITCH TO [dbo].[NEW_tblEmailsSent];
-- drop the original (now empty) table
DROP TABLE [dbo].[tblEmailsSent];
-- rename new table to old table's name
EXEC sp_rename 'NEW_tblEmailsSent','tblEmailsSent';
COMMIT;
After the new table has IDENTITY property you normally should set the current identity value to the maximum of the actual values in your table. If you don't do it, new rows inserted into the table would start from 1.
One way to do it is to run DBCC CHECKIDENT after you switched the tables:
DBCC CHECKIDENT('dbo.tblEmailsSent')
Alternatively, you can specify the new seed in the table definition:
CREATE TABLE [dbo].[NEW_tblEmailsSent](
[id] [int] IDENTITY(<max value of id + 1>, 1) NOT NULL,
Every other article I see has something to with JOINS... I'm not even trying to do a join! I'm just trying to run a simple UPDATE based off information in a temporary table. Here's the code...
BEGIN TRAN ArchiveMigration
-- insert into temporary table
CREATE TABLE #tblTemp(
[theID] [int] NOT NULL,
[ScheduleID] [int] NOT NULL,
[OverridingCustomerID] [int] NOT NULL,
[Timestamp] [datetime] NOT NULL,
[DeviceName] [nvarchar](max) NULL,
[DestinationTempCool] [int] NULL,
[DestinationMode] [nvarchar](max) NULL,
[DestinationTempHeat] [int] NULL,
CONSTRAINT [PK_#tblTemp] PRIMARY KEY CLUSTERED
(
[theID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
INSERT INTO #tblTemp ([theID], [ScheduleID], [OverridingCustomerID], Timestamp, DeviceName, DestinationTempCool, DestinationMode, DestinationTempHeat)
SELECT Id, ScheduleId, OverridingCustomerId, Timestamp, DeviceName, DestinationTempCool, DestinationMode, DestinationTempHeat
FROM CustomerScheduleOverride
WHERE Id = 836;
-- modify the extended info table
UPDATE ExtendedOverrideInfo
SET ExtendedOVerrideInfo.OverrideId = Null
WHERE ExtendedOverrideInfo.OverrideId = #tblTemp.[theID];
COMMIT TRAN
All I want to do is nullify the values of ExtendedOverrideInfo.OverrideId if said ID exists in the #tblTemp (statement is towards the bottom of the script). Any idea why I might be getting this message? Thanks in advanced!
Your current UPDATE syntax is incorrect, you will need to use a JOIN on your temporary table. This article from Pinal Dave provides a more detailed explanation.
UPDATE ExtendedOverrideInfo
SET ExtendedOverrideInfo.OverrideId = Null
FROM ExtendedOverrideInfo
INNER JOIN #tblTemp t on t.[theID]=ExtendedOverrideInfo.OverrideId
You update statment is totally wrong,the where clause is not correct,you have multiple choices here to resolve your problem:
make join with tmptable
use Exists key in your where clause
Or simply,if your purpose of creating tmptable is just to nullify,why not using cursor?or change your where statment to search record by id?
I recently discovered included columns in SQL Server indexes. Do included columns in an index take up extra memory or are they stored on disk?
Also can someone point me to performance implications of including columns of differing data types as included columns in a Primary Key, which in my case is typically an in?
Thanks.
I don't fully understand the question: "Do included columns in an index take up extra memory or are they stored on disk?" Indexes are both stored on disk (for persistence) and in memory (for performance when being used).
The answer to your question is that the non-key columns are stored in the index and hence are stored both on disk and memory, along with the rest of the index. Included columns do have a significant performance advantage over key columns in the index. To understand this advantage, you have to understand the key values may be stored more than once in a b-tree index structure. They are used both as "nodes" in the tree and as "leaves" (the latter point to the actual records in the table). Non-key values are stored only in leaves, providing potentially a big savings in storage.
Such a savings means that more of the index can be stored in memory in a memory-limited environment. And that an index takes up less memory, allowing memory to be used for other things.
The use of included columns is to allow the index to be a "covering" index for queries, with a minimum of additional overhead. An index "covers" a query when all the columns needed for the query are in the index, so the index can be used instead of the original data pages. This can be a significant performance savings.
The place to go to learn more about them is the Microsoft documentation.
In SQL Server 2005 or upper versions, you can extend the functionality of nonclustered indexes by adding nonkey columns to the leaf level of the nonclustered index.
By including nonkey columns, you can create nonclustered indexes that cover more queries. This is because the nonkey columns have the following benefits:
• They can be data types not allowed as index key columns. ( All data types are allowed except text, ntext, and image.)
• They are not considered by the Database Engine when calculating the number of index key columns or index key size. You can include nonkey columns in a nonclustered index to avoid exceeding the current index size limitations of a maximum of 16 key columns and a maximum index key size of 900 bytes.
An index with included nonkey columns can significantly improve query performance when all columns in the query are included in the index either as key or nonkey columns. Performance gains are achieved because the query optimizer can locate all the column values within the index; table or clustered index data is not accessed resulting in fewer disk I/O operations.
Example:
Create Table Script
CREATE TABLE [dbo].[Profile](
[EnrollMentId] [int] IDENTITY(1,1) NOT NULL,
[FName] [varchar](50) NULL,
[MName] [varchar](50) NULL,
[LName] [varchar](50) NULL,
[NickName] [varchar](50) NULL,
[DOB] [date] NULL,
[Qualification] [varchar](50) NULL,
[Profession] [varchar](50) NULL,
[MaritalStatus] [int] NULL,
[CurrentCity] [varchar](50) NULL,
[NativePlace] [varchar](50) NULL,
[District] [varchar](50) NULL,
[State] [varchar](50) NULL,
[Country] [varchar](50) NULL,
[UIDNO] [int] NOT NULL,
[Detail1] [varchar](max) NULL,
[Detail2] [varchar](max) NULL,
[Detail3] [varchar](max) NULL,
[Detail4] [varchar](max) NULL,
PRIMARY KEY CLUSTERED
(
[EnrollMentId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
GO
SET ANSI_PADDING OFF
GO
Stored procedure script
CREATE Proc [dbo].[InsertIntoProfileTable]
As
BEGIN
SET NOCOUNT ON
Declare #currentRow int
Declare #Details varchar(Max)
Declare #dob Date
set #currentRow =1;
set #Details ='Let''s think about the book. Every page in the book has the page number. All information in this book is presented sequentially based on this page number. Speaking in the database terms, page number is the clustered index. Now think about the glossary at the end of the book. This is in alphabetical order and allow you to quickly find the page number specific glossary term belongs to. This represents non-clustered index with glossary term as the key column. Now assuming that every page also shows "chapter" title at the top. If you want to find in what chapter is the glossary term, you have to lookup what page # describes glossary term, next - open corresponding page and see the chapter title on the page. This clearly represents key lookup - when you need to find the data from non-indexed column, you have to find actual data record (clustered index) and look at this column value. Included column helps in terms of performance - think about glossary where each chapter title includes in addition to glossary term. If you need to find out what chapter the glossary term belongs - you don''t need to open actual page - you can get it when you lookup the glossary term. So included column are like those chapter titles. Non clustered Index (glossary) has addition attribute as part of the non-clustered index. Index is not sorted by included columns - it just additional attributes that helps to speed up the lookup (e.g. you don''t need to open actual page because information is already in the glossary index).'
while(#currentRow <=200000)
BEGIN
insert into dbo.Profile values( 'FName'+ Cast(#currentRow as varchar), 'MName' + Cast(#currentRow as varchar), 'MName' + Cast(#currentRow as varchar), 'NickName' + Cast(#currentRow as varchar), DATEADD(DAY, ROUND(10000*RAND(),0),'01-01-1980'),NULL, NULL, #currentRow%3, NULL,NULL,NULL,NULL,NULL, 1000+#currentRow,#Details,#Details,#Details,#Details)
set #currentRow +=1;
END
SET NOCOUNT OFF
END
GO
Using the above SP you can insert 200000 records at one time.
You can see that there is a clustered index on column “EnrollMentId”.
Now Create a non-Clustered index on “ UIDNO” Column.
Script
CREATE NONCLUSTERED INDEX [NonClusteredIndex-20140216-223309] ON [dbo].[Profile]
(
[UIDNO] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
Now Run the following Query
select UIDNO,FName,DOB, MaritalStatus, Detail1 from dbo.Profile --Takes about 30-50 seconds and return 200,000 results.
Query 2
select UIDNO,FName,DOB, MaritalStatus, Detail1 from dbo.Profile
where DOB between '01-01-1980' and '01-01-1985'
--Takes about 10-15 seconds and return 36,479 records.
Now drop the above non-clustered index and re-create with following script
CREATE NONCLUSTERED INDEX [NonClusteredIndex-20140216-231011] ON [dbo].[Profile]
(
[UIDNO] ASC,
[FName] ASC,
[DOB] ASC,
[MaritalStatus] ASC,
[Detail1] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
It will throw the following error
Msg 1919, Level 16, State 1, Line 1
Column 'Detail1' in table 'dbo.Profile' is of a type that is invalid for use as a key column in an index.
Because we can not use varchar(Max) datatype as key column.
Now Create a non-Clustered Index with included columns using following script
CREATE NONCLUSTERED INDEX [NonClusteredIndex-20140216-231811] ON [dbo].[Profile]
(
[UIDNO] ASC
)
INCLUDE ( [FName],
[DOB],
[MaritalStatus],
[Detail1]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
Now Run the following Query
select UIDNO,FName,DOB, MaritalStatus, Detail1 from dbo.Profile --Takes about 20-30 seconds and return 200,000 results.
Query 2
select UIDNO,FName,DOB, MaritalStatus, Detail1 from dbo.Profile
where DOB between '01-01-1980' and '01-01-1985'
--Takes about 3-5 seconds and return 36,479 records.
Included columns provide functionality similar to a clustered index where the row contents are kept in the leaf node of the primary index. In addition to the key columns in the index, additional attributes are kept in the index table leaf nodes.
This permits immediate access to the column values without having to access another page in the database. There is a trade off with increased index size and general storage against the improved response from not having to indirect through a page reference in the index. The impact is likely similar with adding multiple indices to tables.
From here:-
An index with nonkey columns can significantly improve query
performance when all columns in the query are included in the index
either as key or nonkey columns. Performance gains are achieved
because the query optimizer can locate all the column values within
the index; table or clustered index data is not accessed resulting in
fewer disk I/O operations.
I'm creating a database that holds yield values of electric engines. The yield values are stored in an Excel file which I have to transfer to the database. Each test for an engine has 42 rows (torque) and 42 columns (power in kw) with the values stored in these cells.
(kw) 1,0 1,2 ...(42x)
-------- -------
(rpm)2000 76,2 77,0
2100 76,7 77,6
...
(42x)
Well I thought of creating a column for engine_id, test_id (each engine can have more than one test), and 42 columns for the corresponding yield values. For each test I have to add 42 rows for one single engine with the yield values. This doesn't seem efficient nor easy to implement to me.
If there are 42 records (rows) for 1 single engine, in a matter of time the database will hold up several thousands of rows and searching for a specific engine with the corresponding values will be an exhausting task.
If I make for each test for a specific engine a separate table, again after some time I would I have probably thousands of tables. Now what should I go for, a table with thousands of records or a table with 42 columns and 42 rows? Either way, I still have redundant records.
A database is definitely the answer (searching through many millions, or hundred of millions of rows is pretty easy once you get the hang of SQL (the language for interacting with databases). I would recommend a table structure of
EngineId, TestId, TourqueId, PowerId, YieldValue
Which would have values...
Engine1, Test1, 2000, 1.0, 73.2
So only 5 columns. This will give you the flexibility to add more yield results in future should it be required (or even if its not, its just an easier schema anyway). You will need to learn SQL, however, to realise the power of the database over a spreadsheet. Also, there are many techniques for importing Excel data to SQL, so you should investigate that (Google it). If you find you are transferring all that data by hand then you are doing something wrong (not wrong really, but inefficient!).
Further to your comments, here is the exact schema with index (in MS SQL Server)
CREATE TABLE [dbo].[EngineTestResults](
[EngineId] [varchar](50) NOT NULL,
[TestId] [varchar](50) NOT NULL,
[Tourque] [int] NOT NULL,
[Power] [decimal](18, 4) NOT NULL,
[Yield] [decimal](18, 4) NOT NULL,
CONSTRAINT [PK_EngineTestResults] PRIMARY KEY CLUSTERED
(
[EngineId] ASC,
[TestId] ASC,
[Tourque] ASC,
[Power] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
SET ANSI_PADDING OFF
GO
/****** Object: Index [IX_EngineTestResults] Script Date: 01/14/2012 14:26:21 ******/
CREATE NONCLUSTERED INDEX [IX_EngineTestResults] ON [dbo].[EngineTestResults]
(
[EngineId] ASC,
[TestId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
So note that there is no incrementing primary key...the key is (EngineId, TestId, Torque, Power). To get the results for a particular engine you would run a query like the following:
Select * from EngineTestResults where engineId = 'EngineABC' and TestId = 'TestA'
Note that I have added an index for that set of criteria.
The strength of a relational database is the ability to normalize data across multiple tables, so you could have one table for engines, one for tests and one for results. Something like the following:
CREATE TABLE tbl__engines (
`engine_id` SMALLINT UNSIGNED NOT NULL,
`name` VARCHAR(255) NOT NULL,
PRIMARY KEY(engine_id)
);
CREATE TABLE tbl__tests (
`test_id` INT UNSIGNED NOT NULL,
`engine_id` SMALLINT UNSIGNED NOT NULL,
PRIMARY KEY(test_id),
FOREIGN KEY(engine_id) REFERENCES tbl__engines(engine_id)
);
CREATE TABLE tbl__test_result (
`result_id` INT UNSIGNED NOT NULL,
`test_id` INT UNSIGNED NOT NULL,
`torque` INT NOT NULL,
`power` DECIMAL(6,2) NOT NULL,
`yield` DECIMAL(6,2) NOT NULL,
FOREIGN KEY(test_id) REFERENCES tbl__tests(test_id)
);
Then you can simply perform a join across these three tables to return the required results. Something like:
SELECT
*
FROM `tbl__engines` e
INNER JOIN `tbl__tests` t ON e.engine_id = t.engine_id
INNER JOIN `tbl__results` r ON r.test_id = t.test_id;