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What is the accepted practice for indenting SQL statements? For example, consider the following SQL statement:
SELECT column1, column2
FROM table1
WHERE column3 IN
(
SELECT TOP(1) column4
FROM table2
INNER JOIN table3
ON table2.column1 = table3.column1
)
How should this be indented? Many thanks.
SELECT column1
, column2
FROM table1
WHERE column3 IN
(
SELECT TOP(1) column4
FROM table2
INNER JOIN table3
ON table2.column1 = table3.column1
)
I like to have all "," in front, this way I never search them when an error at line X from the SQL editor.
This is an example for those who do not use this type of writting SQL statement. Both contain an error of a missing comma.
SELECT sdcolumn123
, dscolumn234
, sdcolumn343
, ffcolumn434
, sdcolumn543
, bvcolumn645
vccolumn754
, cccolumn834
, vvcolumn954
, cvcolumn104
FROM table1
WHERE column3 IN
(
...
)
SELECT sdcolumn123, dscolumn234, asdcolumn345, dscolumn456, ascolumn554, gfcolumn645 sdcolumn754, fdcolumn845, sdcolumn954, fdcolumn1054
FROM table1
WHERE column3 IN
(
...
)
I found easier and more quick at the first example. Hope this example show you more my point of view.
SELECT column1, column2
FROM table
WHERE column3 IN (
SELECT TOP(1) column4
FROM table2
INNER JOIN table3 ON table2.column1 = table3.column1
)
This is pretty short and easy to read. I'd make adjustments if there were more columns selected or more join conditions.
Not sure there is an accepted practice, but here's now how I'd do it:
SELECT
column1,
column2
FROM
table1
WHERE
column3 IN
(
SELECT TOP(1)
column4
FROM
table2
INNER JOIN
table3
ON table2.column1 = table3.column1
)
I like to have "rivers" of white space in the code. It makes it a little easier to scan.
SELECT column1,
column2
FROM table1
WHERE column3 IN (SELECT column4
FROM table2
JOIN table3
ON table2.column1 = table3.column1);
I like jalbert's form of lining up the keywords on their right. I'd also add that I like the ANDs and ORs on the left (some people put them on the right.) In addition, I like to line up my equals signs when possible.
SELECT column1,
column2
FROM table1, table2
WHERE table1.column1 = table2.column4
AND table1.col5 = "hi"
OR table2.myfield = 678
This is my personal method. Depending on the length of the join condition I sometimes indent it on the line below.
SELECT
column1,
column2
FROM
table1
WHERE
column3 IN (
SELECT TOP(1)
column4
FROM
table2
INNER JOIN table3 ON table2.column1 = table3.column1
)
SELECT
column1,
column2
FROM
table1
WHERE
column3 IN (
SELECT TOP(1)
column4
FROM
table2
INNER JOIN table3
ON table2.column1 = table3.column1 -- for long ones
)
I've written a code standard for our shop that is biased in the extreme towards readability/"discoverability" (the latter being primarily useful in insert-select statements):
SELECT
column1,
column2
FROM
table1
WHERE
column3 IN
(
SELECT TOP(1)
column4
FROM
table2
INNER JOIN table3 ON table2.column1 = table3.column1
)
On more complex queries it becomes more obvious how this is useful:
SELECT
Column1,
Column2,
Function1
(
Column1,
Column2
) as Function1,
CASE
WHEN Column1 = 1 THEN
a
ELSE
B
END as Case1
FROM
Table1 t1
INNER JOIN Table2 t2 ON t1.column12 = t2.column21
WHERE
(
FilterClause1
AND FilterClause2
)
OR
(
FilterClause3
AND FilterClause4
)
Once you move to systems with more than a single join in most of your queries, it has been my experience that using vertical space liberally is your best friend with complex SQL.
SQL formatting is an area where there is a great deal of variance and disagreement... But fwiw, I like to focus on readability and think that whatever you do, consistently conforming to any rules that reduce readability is, as the old cliche goes, a "foolish consistency" ( "Foolish consistency is a hobgoblin for simple minds" )
So, instead of calling them rules, here are some guidelines.
For each Major clause in a SQL statement (Select, Insert, Delete, From, Where, Having, Group BY, Order By, ... I may be missing a few) should be EASILY identifiable. So I generally indent them at the highest level, all even with each other. Then within each clause, I indent the next logical sub structure evenly... and so on.. But I feel free to (and often do) change the pattern if in any individual case it would be more readable to do so... Complex Case statements are a good example. Because anything that requires horizontal scrolling reduces readability enormously, I often write complex (nested) Case expressions on multiple lines. When I do, I try to keep the beginning of such a statement hanging indent based on it's logical place in the SQL statement, and indent the rest of the statement lines a few characters furthur...
SQL Database code has been around for a long time, since before computers had lower case, so there is a historical preference for upper casing keywords, but I prefer readability over tradition... (and every tool I use color codes the key words now anyway)
I also would use Table aliases to reduce the amount of text the eye has to scan in order to grok the structure of the query, as long as the aliases do not create confusion. In a query with less than 3 or 4 tables, Single character aliases are fine, I often use first letter of the table if all ther tables start with a different letter... again, whatever most contributes to readability. Finally, if your database supports it, many of the keywords are optional, (like "Inner", "Outer", "As" for aliases, etc.) "Into" (from Insert Into) is optional on Sql Server - but not on Oracle) So be careful about using this if your code needs to be platform independant...
Your example, I would write as:
Select column1, column2
From table1 T1
Where column3 In (Select Top(1) column4
From table2 T2
Join table3 T3
On T2.column1 = T3.column1)
Or
Select column1, column2
From table1 T1
Where column3 In
(Select Top(1) column4
From table2 T2
Join table3 T3
On T2.column1 = T3.column1)
If there many more columns on the select clause, I would indent the second and subsequent lines... I generally do NOT adhere to any strict (one column per row) kind of rule as scrolling veritcally is almost as bad for readability as scrolling horizontally is, especially if only the first ten columns of the screen have any text in them)
Select column1, column2, Col3, Col4, column5,
column6, Column7, isNull(Column8, 'FedEx') Shipper,
Case Upper(Column9)
When 'EAST' Then 'JFK'
When 'SOUTH' Then 'ATL'
When 'WEST' Then 'LAX'
When 'NORTH' Then 'CHI' End HubPoint
From table1 T1
Where column3 In
(Select Top(1) column4
From table2 T2
Join table3 T3
On T2.column1 = T3.column1)
Format the code in whatever manner makes it the most readable...
If you have a lengthy SQL statement that you'd like to reformat without all the typing and tabbing, you can slap it into this website and get a nicely formatted result. You can experiment with various formats to see which makes your text the most readable.
Edit: I believe that this is the 2014 location of the SQL formatter.
Here's my poke at this:
select column1, column2
from table1
where (column3 in (
select top(1) column4
from table2
inner join table3
on (table2.column1 = table3.column1)
))
;
Everything lowercase because it's easier to read lowercase characters (and we have code highlighting to emphasize keywords) also easier to type
Every restriction or option on a keyword (like the from on the select or the on on the join) is indented to show their dependance on the outward keyword
The closing bracket is at the same indenting level as the opening where
Use brackets for where- and on-clauses to increase readability
Have the semicolon closing the select-statement at the same indenting so multiple statements can be distinguished better (if you need a semicolon in your language like SAS PROC SQL does)
It's still quite compact and does not stretch all over the page
I like to have the different parts of my query line up vertically. I tend to use a tab size of 8 spaces for SQL which seems to work well.
SELECT column1,
column2
FROM table1
WHERE column3 IN
(
SELECT TOP(1) column4
FROM table2
INNER JOIN table3
ON table2.column1 = table3.column1
)
Example indenting a very very very complex SQL:
SELECT
produtos_cesta.cod_produtos_cesta,
produtos.nome_pequeno,
tab_contagem.cont,
produtos_cesta.sku,
produtos_kits.sku_r AS sku_kit,
sku_final = CASE
WHEN produtos_kits.sku_r IS NOT NULL THEN produtos_kits.sku_r
ELSE produtos_cesta.sku
END,
estoque = CASE
WHEN produtos2.estoque IS NOT NULL THEN produtos2.estoque
ELSE produtos.estoque
END,
produtos_cesta.unidades as unidades1,
unidades_x_quantidade = CASE
WHEN produtos.cod_produtos_kits_tipo = 1 THEN CAST(produtos_cesta.quantidade * (produtos_cesta.unidades / tab_contagem.cont) * produtos_kits.quantidade AS int)
ELSE CAST(produtos_cesta.quantidade * produtos_cesta.unidades AS int)
END,
unidades = CASE
WHEN produtos.cod_produtos_kits_tipo = 1 THEN produtos_cesta.unidades / tab_contagem.cont * produtos_kits.quantidade
ELSE produtos_cesta.unidades
END,
unidades_parent = produtos_cesta.unidades,
produtos_cesta.quantidade,
produtos.controla_estoque,
produtos.status
FROM
produtos_cesta
INNER JOIN produtos
ON (produtos_cesta.sku = produtos.sku)
INNER JOIN produtos_pacotes
ON (produtos_cesta.sku = produtos_pacotes.sku)
INNER JOIN (
SELECT
produtos_cesta.cod_produtos_cesta,
cont = SUM(
CASE
WHEN produtos_kits.quantidade IS NOT NULL THEN produtos_kits.quantidade
ELSE 1
END
)
FROM
produtos_cesta
LEFT JOIN produtos_kits
ON (produtos_cesta.sku = produtos_kits.sku)
LEFT JOIN produtos
ON (produtos_cesta.sku = produtos.sku)
WHERE
shopper_id = '" + mscsShopperId + #"'
GROUP BY
produtos_cesta.cod_produtos_cesta,
produtos_cesta.sku,
produtos_cesta.unidades
)
AS tab_contagem
ON (produtos_cesta.cod_produtos_cesta = tab_contagem.cod_produtos_cesta)
LEFT JOIN produtos_kits
ON (produtos.sku = produtos_kits.sku)
LEFT JOIN produtos as produtos2
ON (produtos_kits.sku_r = produtos2.sku)
WHERE
shopper_id = '" + mscsShopperId + #"'
GROUP BY
produtos_cesta.cod_produtos_cesta,
tab_contagem.cont,
produtos_cesta.sku,
produtos_kits.sku_r,
produtos.cod_produtos_kits_tipo,
produtos2.estoque,
produtos.controla_estoque,
produtos.estoque,
produtos.status,
produtos.nome_pequeno,
produtos_cesta.unidades,
produtos_cesta.quantidade,
produtos_kits.quantidade
ORDER BY
produtos_cesta.sku,
produtos_cesta.unidades DESC
As most above have lined up the return column names, I find lining up tables names and conditions helps readability a lot.
SELECT
column1,
column2
FROM
table1
WHERE
column3 IN
(
SELECT TOP(1)
column4
FROM
table2 INNER JOIN
table3 ON table2.column1 = table3.column1
)
And for when join conditions get long.
SELECT
Column1,
Column2
FROM
Table1 JOIN
Table2 ON
Table1.Column3 = Table2.Column4 JOIN
Table3 ON
Table2.Column1 = Table3.Column1 and
Table2.ColumnX = #x and
Table3.ColumnY = #y
WHERE
Condition1=xxx and
Condition2=yyy and
(
Condition3=aaa or
Condition4=bbb
)
Of course, this comes down to personal preference. And if in a team setting, it's something that should be agreed upon among the members for consistency's sake. But this would be my preference:
SELECT column1, column2
FROM table1
WHERE column3 IN(SELECT TOP(1) column4
FROM table2
INNER JOIN table3 ON
table2.column1 = table3.column1
)
I would format like this:
SELECT
column1,
column2
FROM
table1
WHERE
column3 IN (SELECT TOP(1)
column4
FROM
table2
INNER JOIN table3 ON table2.column1 = table3.column1)
or like this:
SELECT
column1,
column2
FROM
table1
WHERE
column3 IN (SELECT TOP(1) column4
FROM table2
INNER JOIN table3 ON table2.column1 = table3.column1)
Well, of course it depends on the query.
For simple queries, a highly formal indentation scheme is just more trouble than it's worth and can actually make the code less readable, not more. But as complexity grows you need to start being more careful with how you structure the statement, to make sure it will be readable again later.
I've just put it through my SQL prettifier and it came out like this....
SELECT column1, column2
FROM table1
WHERE column3 IN
(
SELECT TOP(1) column4
FROM table2
INNER JOIN table3
ON table2.column1 = table3.column1
)
http://extras.sqlservercentral.com/prettifier/prettifier.aspx
.....But I haven't worked out a way of getting colours into StackOverflow.
Yeah, this is pretty subjective...But here's my 2 cents:
SELECT
Column1,
Column2
FROM Table1
WHERE
Column3 IN (
SELECT Column4
FROM Table2
JOIN Table3 ON
Table2.Column1 = Table3.Column1
)
But, really, I'd probably rewrite it without the IN:
SELECT
Column1,
Column2
FROM Table1
JOIN Table2 ON
Table1.Column3 = Table2.Column4
JOIN Table3 ON
Table2.Column1 = Table3.Column1
Basically, my rules are:
Capitalize Keywords
Columns go on individual lines, but SELECT modifiers (SELECT TOP 100, SELECT DISTINCT, etc.) or single columns (SELECT 1, SELECT Id, SELECT *, etc.) go on same line
Join conditions indented underneath JOIN clause
Use JOIN for INNER JOIN (since it's the common one), and fully specify others (LEFT OUTER JOIN, FULL OUTER JOIN, etc.)
Open parens on same line, close paren on separate line. If you have an alias, the alias goes with close paren.
This is my normal preference:
SELECT column1
,column2
FROM table1
WHERE column3 IN (
SELECT TOP(1) column4
FROM table2
INNER JOIN table3
ON table2.column1 = table3.column1
)
I don't know if there's a standard but I like to do it this way;
SELECT column1, column2
FROM table1
WHERE column3 IN
(
SELECT TOP(1) column4
FROM table2
INNER JOIN table3
ON table2.column1 = table3.column1
)
because I can read and analyze the SQL better.
SELECT
Column1,
Column2
FROM
Table1
WHERE
Column3 IN
(
SELECT TOP (1)
Column4
FROM
Table2
INNER JOIN
Table3
ON
Table2.Column1 = Table3.Column1
)
What I usually do is,
print("SELECT column1, column2
FROM table1
WHERE column3 IN (SELECT TOP(1) column4
FROM table2 INNER JOIN
table3 ON table2.column1 = table3.column1)");
This is a matter of taste.
This is my preference.
SELECT
column1
,column2
FROM
table1
WHERE column3 IN (
SELECT TOP(1) column4
FROM
table2
INNER JOIN table3
ON table2.column1 = table3.column1
)
That's how we would do it here:
select
COLUMN1,
COLUMN2,
case when COLUMN5 = 'X'
and
COLUMN6 = 'Y'
then 'one'
when COLUMN5 in (
'AAA',
'BBB'
)
then 'two'
else 'three'
end as COLUMN7
from
TABLE1
where
COLUMN2 in (
select top(1)
COLUMN4
from
TABLE2
inner join
TABLE3
on
TABLE2.COLUMN1 = TABLE3.COLUMN1
and
TABLE2.COLUMN2
between
TABLE3.COLUMN2
and
TABLE3.COLUMN3
)
Our idea is: keep sql keywords in lower case and put all changing (and therefore "more interesting") things like table or column names in upper case.
The code might look a bit "blown up" here, but it increases readability if you have complex queries with longer names (incl. schema etc.) much longer than in this example.
And: indent all objects according to their "level".
Here is my situation:
Table one contains a set of data that uses an id for an unique identifier. This table has a one to many relationship with about 6 other tables such that.
Given Table 1 with Id of 001:
Table 2 might have 3 rows with foreign key: 001
Table 3 might have 12 rows with foreign key: 001
Table 4 might have 0 rows with foreign key: 001
Table 5 might have 28 rows with foreign key: 001
I need to write a report that lists all of the rows from Table 1 for a specified time frame followed by all of the data contained in the handful of tables that reference it.
My current approach in pseudo code would look like this:
select * from table 1
foreach(result) {
print result;
select * from table 2 where id = result.id;
foreach(result2) {
print result2;
}
select * from table 3 where id = result.id
foreach(result3) {
print result3;
}
//continued for each table
}
This means that the single report can run in the neighbor hood of 1000 queries. I know this is excessive however my sql-fu is a little weak and I could use some help.
LEFT OUTER JOIN Tables2-N on Table1
SELECT Table1.*, Table2.*, Table3.*, Table4.*, Table5.*
FROM Table1
LEFT OUTER JOIN Table2 ON Table1.ID = Table2.ID
LEFT OUTER JOIN Table3 ON Table1.ID = Table3.ID
LEFT OUTER JOIN Table4 ON Table1.ID = Table4.ID
LEFT OUTER JOIN Table5 ON Table1.ID = Table5.ID
WHERE (CRITERIA)
Join doesn't do it for me. I hate having to de-tangle the data on the client side. All those nulls from left-joining.
Here's a set-based solution that doesn't use Joins.
INSERT INTO #LocalCollection (theKey)
SELECT id
FROM Table1
WHERE ...
SELECT * FROM Table1 WHERE id in (SELECT theKey FROM #LocalCollection)
SELECT * FROM Table2 WHERE id in (SELECT theKey FROM #LocalCollection)
SELECT * FROM Table3 WHERE id in (SELECT theKey FROM #LocalCollection)
SELECT * FROM Table4 WHERE id in (SELECT theKey FROM #LocalCollection)
SELECT * FROM Table5 WHERE id in (SELECT theKey FROM #LocalCollection)
Ah! Procedural! My SQL would look like this, if you needed to order the results from the other tables after the results from the first table.
Insert Into #rows Select id from Table1 where date between '12/30' and '12/31'
Select * from Table1 t join #rows r on t.id = r.id
Select * from Table2 t join #rows r on t.id = r.id
--etc
If you wanted to group the results by the initial ID, use a Left Outer Join, as mentioned previously.
You may be best off to use a reporting tool like Crystal or Jasper, or even XSL-FO if you are feeling bold. They have things built in to handle specifically this. This is not something the would work well in raw SQL.
If the format of all of the rows (the headers as well as all of the details) is the same, it would also be pretty easy to do it as a stored procedure.
What I would do: Do it as a join, so you will have the header data on every row, then use a reporting tool to do the grouping.
SELECT * FROM table1 t1
INNER JOIN table2 t2 ON t1.id = t2.resultid -- this could be a left join if the table is not guaranteed to have entries for t1.id
INNER JOIN table2 t3 ON t1.id = t3.resultid -- etc
OR if the data is all in the same format you could do.
SELECT cola,colb FROM table1 WHERE id = #id
UNION ALL
SELECT cola,colb FROM table2 WHERE resultid = #id
UNION ALL
SELECT cola,colb FROM table3 WHERE resultid = #id
It really depends on the format you require the data in for output to the report.
If you can give a sample of how you would like the output I could probably help more.
Join all of the tables together.
select * from table_1 left join table_2 using(id) left join table_3 using(id);
Then, you'll want to roll up the columns in code to format your report as you see fit.
What I would do is open up cursors on the following queries:
SELECT * from table1 order by id
SELECT * from table1 r, table2 t where t.table1_id = r.id order by r.id
SELECT * from table1 r, table3 t where t.table1_id = r.id order by r.id
And then I would walk those cursors in parallel, printing your results. You can do this because all appear in the same order. (Note that I would suggest that while the primary ID for table1 might be named id, it won't have that name in the other tables.)
Do all the tables have the same format? If not, then if you have to have a report that can display the n different types of rows. If you are only interested in the same columns then it is easier.
Most databases have some form of dynamic SQL. In that case you can do the following:
create temporary table from
select * from table1 where rows within time frame
x integer
sql varchar(something)
x = 1
while x <= numresults {
sql = 'SELECT * from table' + CAST(X as varchar) + ' where id in (select id from temporary table'
execute sql
x = x + 1
}
But I mean basically here you are running one query on your main table to get the rows that you need, then running one query for each sub table to get rows that match your main table.
If the report requires the same 2 or 3 columns for each table you could change the select * from tablex to be an insert into and get a single result set at the end...