I am currently running this SQL
SELECT jm_recipe.name, jm_recipe.slug
FROM jm_recipe
LEFT JOIN jm_category_recipe ON jm_category_recipe.recipe_id = jm_recipe.id
WHERE jm_category_recipe.category_id = $cat"
This returns the desired results except that I also need to return the name of the category that the recipe I am looking for is in, to do this I tried to add the field in to my SELECT statement and also add the table into the FROM clause,
SELECT jm_recipe.name, jm_recipe.slug, jm_category_name
FROM jm_recipe, jm_category
LEFT JOIN jm_category_recipe ON jm_category_recipe.recipe_id = jm_recipe.id
WHERE jm_category_recipe.category_id = $cat"
However this just returns no results, what am i doing wrong?
You need to join both tables:
SELECT jm_recipe.name, jm_recipe.slug, jm.category_name
FROM jm_recipe
INNER JOIN jm_category_recipe ON jm_category_recipe.recipe_id = jm_recipe.id
INNER JOIN jm_category ON jm_recipe.recipe_id = jm_category.recipe_id
WHERE jm_category_recipe.category_id = $cat
I've changed the joins to inner joins as well. You might want to make them both LEFT joins if you have NULLs and want them in the result.
Also, you're vulnerable to SQL Injection by simply copying over $cat.
Here's some PHP specific info for you (I'm assuming you're using PHP.)
Related
I have the following query:
SELECT games_atp.ID1_G, odds_atp.K1
FROM games_atp LEFT JOIN odds_atp ON (games_atp.ID1_G = odds_atp.ID1_O) AND (games_atp.ID2_G = odds_atp.ID2_O) AND (games_atp.ID_T_G = odds_atp.ID_T_O) AND (games_atp.ID_R_G = odds_atp.ID_R_O)
I know the joining is convoluted but the original db is built without a primary key. The above works fine and importantly pulls all the records from games_atp. I now want to add a criteria into this to pull only certain K1 records from odds_atp. I added a WHERE clause as follows:
SELECT games_atp.ID1_G, odds_atp.K1
FROM games_atp LEFT JOIN odds_atp ON (games_atp.ID1_G = odds_atp.ID1_O) AND (games_atp.ID2_G = odds_atp.ID2_O) AND (games_atp.ID_T_G = odds_atp.ID_T_O) AND (games_atp.ID_R_G = odds_atp.ID_R_O)
WHERE (((odds_atp.ID_B_O)=2));
However, this overides the left join and only pulls records from games_atp where there is a corresponding record in odds_atp with ID_B_O = 2. How do I keep the criteria and all the records in games_atp? Thanks in advance.
Your current where condition will filter your final result, hence you are only seeing id_B_O = 2.
However, you could also add the wehre condition directly into your left join.
something like this.
SELECT
games_atp.ID1_G, odds_atp.K1
FROM
games_atp
LEFT JOIN odds_atp ON
(
(odds_atp.ID_B_O =2)
AND
(
(games_atp.ID1_G = odds_atp.ID1_O)
AND (games_atp.ID2_G = odds_atp.ID2_O)
AND (games_atp.ID_T_G = odds_atp.ID_T_O)
AND (games_atp.ID_R_G = odds_atp.ID_R_O)
)
);
or you could also take advantage of sub-queries
How to write this query in codeigniter
SELECT U.username,U.user_id
FROM storylikes S, user U
WHERE U.user_id=S.user_id_fk AND S.user_id_fk='$id'
try this :
$this->db->select('u.username, u.user_id');
db->where('u. user_id = s.user_id_fk');
$this->db->where('s.user_id_fk = '.$id);
$query = $this->db->get('storylikes s, user u');
use $your_variable = $query->result(); for the result
you should use joins instead of this query
$this->db->select('username,user_id');
$this->db->from('user');
$this->db->join('storylike','storylike.user_id_fk = user.user_id');
$this->db->where('storylike.user_id','$id');
as long as the db helper is loaded... You dont need to do anything special
$query = $this->db->query('SELECT U.username,U.user_id FROM storylikes S, user U WHERE U.user_id=S.user_id_fk AND S.user_id_fk=$id);
Using a cartesian (cross join) by doing FROM with 2 tables can cause some unruly results if not used 'correctly'
I suggest that if you are trying to just join tables together your SQL should be
SELECT U.username,U.user_id
FROM storylikes S, user U
INNER JOIN user U ON S.user_id = U.user_id_fk
WHERE S.user_id_fk=$id
CI querybuilder for this would be:
$query = $this->db->select('U.username,U.user_id')
->join('user U', 'S.user_id = U.user_id_fk', 'inner')
->where('S.user_id', $id)
->get('user U');
Using the correct join for the correct requirements is key;
INNER JOIN to ensure both FROM and the JOIN table match 1 for 1...
LEFT JOIN if you want to ensure you have all data from your FROM table and any without results in the JOIN table show up as NULL
RIGHT JOIN (opposite of left), to grab all data from the JOIN table and only matching data from the FROM table.
CROSS (CARTESIAN) JOIN when you want to ... frankly... mash the data together... A CROSS JOIN will also function like an INNER JOIN when you stipulate criteria in the WHERE statement (like you did) but still, use the correct JOIN for the correct usage-case.
There are other available joins but those are the basics.
I have two tables named DE1_0_2008_TO_2010_OUTPATIENT_CLAIMS_SAMPLE_1 and DE1_0_2008_BENEFICIARY_SUMMARY_FILE_SAMPLE_1 in the same database.
I have to perform a query on DE1_0_2008_TO_2010_OUTPATIENT_CLAIMS_SAMPLE_1 and then perform the LEFT JOIN of this queried result with `DE1_0_2008_BENEFICIARY_SUMMARY_FILE_SAMPLE_1'. The query alone results in 1178 rows which is fine. But I am not able to do the LEFT JOIN. I used this SQL query:
SELECT *
FROM `DE1_0_2008_TO_2010_OUTPATIENT_CLAIMS_SAMPLE_1`
LEFT JOIN DE1_0_2008_BENEFICIARY_SUMMARY_FILE_SAMPLE_1
ON DE1_0_2008_TO_2010_OUTPATIENT_CLAIMS_SAMPLE_1.DESYNPUF_ID = DE1_0_2008_BENEFICIARY_SUMMARY_FILE_SAMPLE_1.DESYNPUF_ID
WHERE DE1_0_2008_TO_2010_OUTPATIENT_CLAIMS_SAMPLE_1.ICD9_DGNS_CD_1 = 7243 OR DE1_0_2008_TO_2010_OUTPATIENT_CLAIMS_SAMPLE_1.ICD9_DGNS_CD_2 = 7243 OR DE1_0_2008_TO_2010_OUTPATIENT_CLAIMS_SAMPLE_1.ICD9_DGNS_CD_3 = 7243 OR ICD9_DGNS_CD_4 = 7243
This query is technically fine.
Note that it can be rewritten more elegantly as follows, but really you need to take a closer look at both partitioning and, crucially, normalisation...
SELECT *
FROM DE1_0_2008_TO_2010_OUTPATIENT_CLAIMS_SAMPLE_1 o
LEFT
JOIN DE1_0_2008_BENEFICIARY_SUMMARY_FILE_SAMPLE_1 b
ON o.DESYNPUF_ID = b.DESYNPUF_ID
WHERE 7243 IN(o.ICD9_DGNS_CD_1,o.ICD9_DGNS_CD_2,o.ICD9_DGNS_CD_3,o.ICD9_DGNS_CD_4);
So, this query is currently used in a webshop to retrieve technical data about articles.
It has served its purpose fine except the amount of products shown have increased lately resulting in unacceptable long loading times for some categories.
For one of the worst pages this (and some other queries) get requested about 80 times.
I only recently learned that MySQL does not optimize sub-queries that don't have a depending parameter to only run once.
So if someone could help me with one of the queries and explain how you can replace the in's and exists's to joins, i will probably be able to change the other ones myself.
select distinct criteria.cri_id, des_texts.tex_text, article_criteria.acr_value, article_criteria.acr_kv_des_id
from article_criteria, designations, des_texts, criteria, articles
where article_criteria.acr_cri_id = criteria.cri_id
and article_criteria.acr_art_id = articles.art_id
and articles.art_deliverystatus = 1
and criteria.cri_des_id = designations.des_id
and designations.des_lng_id = 9
and designations.des_tex_id = des_texts.tex_id
and criteria.cri_id = 328
and article_criteria.acr_art_id IN (Select distinct link_art.la_art_id
from link_art, link_la_typ
where link_art.la_id = link_la_typ.lat_la_id
and link_la_typ.lat_typ_id = 17484
and link_art.la_ga_id IN (Select distinct link_ga_str.lgs_ga_id
from link_ga_str, search_tree
where link_ga_str.lgs_str_id = search_tree.str_id
and search_tree.str_type = 1
and search_tree.str_id = 10132
and EXISTS (Select *
from link_la_typ
where link_la_typ.lat_typ_id = 17484
and link_ga_str.lgs_ga_id = link_la_typ.lat_ga_id)))
order by article_criteria.acr_value
I think this one is the main badguy with sub-sub-sub-queries
I just noticed i can remove the last exist and still get the same results but with no increase in speed, not part of the question though ;) i'll figure out myself whether i still need that part.
Any help or pointers are appreciated, if i left out some useful information tell me as well.
I think this is equivalent:
SELECT DISTINCT c.cri_id, dt.tex_text, ac.acr_value, ac.acr_kv_des_id
FROM article_criteria AS ac
JOIN criteria AS c ON ac.acr_cri_id = c.cri_id
JOIN articles AS a ON ac.acr_art_id = a.art_id
JOIN designations AS d ON c.cri_des_id = d.des_id
JOIN des_texts AS dt ON dt.tex_id = d.des_tex_id
JOIN (SELECT distinct la.la_art_id
FROM link_art AS la
JOIN link_la_typ AS llt ON la.la_id = llt.lat_la_id
JOIN (SELECT DISTINCT lgs.lgs_ga_id
FROM link_ga_str AS lgs
JOIN search_tree AS st ON lgs.lgs_str_id = st.str_id
JOIN link_la_typ AS llt ON lgs.lgs_ga_id = llt.lat_ga_id
WHERE st.str_type = 1
AND st.str_id = 10132
AND llt.lat_typ_id = 17484) AS lgs
ON la.la_ga_id = lgs.lgs_ga_id
WHERE llt.lat_typ_id = 17484) AS la
ON ac.acr_art_id = la.la_art_id
WHERE a.art_deliverystatus = 1
AND d.des_lng_id = 9
AND c.cri_id = 328
ORDER BY ac.acr_value
All the IN <subquery> clauses can be replaced with JOIN <subquery>, where you then JOIN on the column being tested equaling the column returned by the subquery. And the EXISTS test is converted to a join with the table, moving the comparison in the subquery's WHERE clause into the ON clause of the JOIN.
It's probably possible to flatten the whole thing, instead of joining with subqueries. But I suspect performance will be poor, because this won't reduce the temporary tables using DISTINCT. So you'll get combinatorial explosion in the resulting cross product, which will then have to be reduced at the end with the DISTINCT at the top.
I've converted all the implicit joins to ANSI JOIN clauses, to make the structure clearer, and added table aliases to make things more readable.
In general, you can convert a FROM tab1 WHERE ... val IN (SELECT blah) to a join like this.
FROM tab1
JOIN (
SELECT tab1_id
FROM tab2
JOIN tab3 ON whatever = whatever
WHERE whatever
) AS sub1 ON tab1.id = sub1.tab1_id
The JOIN (an inner join) will drop the rows that don't match the ON condition from your query.
If your tab1_id values can come up duplicate from your inner query, use SELECT DISTINCT. But don't use SELECT DISTINCT unless you need to; it is costly to evaluate.
Is it possible to write this sql query without alias? I am using a PHP script that doesn't covers alias so I have problem with that.
If this is possible please provide me with some help
This is the code:
SELECT
time1.Time, time2.Time, time1.Signal, v.name, v.lastname, k.vehicle, time1.Reg
FROM
data time1
INNER JOIN data time2
ON time1.id != time2.id
AND time1.serial= time2.serial
INNER JOIN drivers v
ON time1.FK_ID_driver=v.ID_driver
INNER JOIN vehicles k
ON time1.Reg=k.Reg
WHERE
TIMEDIFF(time2.Time, time1.Time) BETWEEN '00:15:00' AND '00:30:00';
You can't easily achieve what you want, since you are joining the same table twice, and SQL needs an alias to disambiguate them.
You could, however, create a view for table data, and use the view instead of the table name in one of the data joins.
Example:
select data.time,
vData.time,
data.Signal,
drivers.name,
drivers.lastname,
vehicles.vehicle,
data.Reg
from data
inner join vData on data.id != vData.id and data.serial = vData.serial
inner join drivers on data.FK_ID_driver = drivers.ID_driver
inner join vehicles on data.Reg = vehicles.Reg
where TIMEDIFF(vData.time, data.time) between '00:15:00' and '00:30:00';