将复杂的SQL转换为JOIN

Question

I have the following SQL statement. Which is working okay. Except in some cases the processing of the query takes a lot of time, resulting in a system time out. So I need to convert the statement. Probably with a JOIN.

I can't figure out how to convert this statement:

SELECT table1.id as id, 
       table1.firstname, 
       table1.lastname, 
       table3.name, 
       table4.name 

FROM table1, table2, table3, table4, table5 

WHERE table1.id = table2.tabel1id 
AND table2.table2id = table3.table2id 
AND table3.table3id = table5.table3id
AND table5.somecode = '5' 
AND table3.table3id = table4.name 
AND table1.firstname LIKE '%John%' 

GROUP BY table1.id 
ORDER BY table3.name, table1.firstname, table1.lastname

I have the nesting of the tables and I also want to use the results of subqueries in the final SELECT (table3.name and table4.name)

Answer 1

You already have JOINs, but you use the implicit version (comma-delimited table list in FROM plus join-conditions in WHERE) instead of the explicit (JOIN plus ON).

So rewriting should not improve performance (otherwise MySQL is more crappy than I thought).

You should better check if you created all neccessary indexes.

Answer 2

SELECT table1.id as id, 
       table1.firstname, 
       table1.lastname, 
       table3.name, 
       table4.name 

FROM table1 INNER JOIN table2
ON table1.id = table2.tabel1id 
INNER JOIN  table3 
ON table2.table2id = table3.table2id
INNER JOIN  table4
ON table3.table3id = table4.name 
INNER JOIN table5 
ON table3.table3id = table5.table3id
WHERE 
     table5.somecode = '5' 
AND table1.firstname LIKE '%John%' 

GROUP BY table1.id as id, 
       table1.firstname, 
       table1.lastname, 
       table3.name, 
       table4.name 
ORDER BY table3.name, table1.firstname, table1.lastname

Read Here for more information about sql server JOIN syntax

Answer 3

select t1.id,t1.firstname,t3.name,t4.name 
from table1 as t1 
inner join table2 as t2 on t1.id=t2.tabel1id 
inner join on table3 as t3 on t2.table2id=t3.table2id
inner join on table4 as t4 on t3.table3id=t4.name
inner join on table5 as t5 on t5.table3id=table3.table3id 
where t1.firstname like '%John%' and t5.somecode='5'
group by t1.id
order by t3.name,t1.firstname,t1.lastname