Develop Reference

Android SQLite additional WHERE condition after MATCH

In Android SQLite i got tabel like this
domainObjectId: String // like '9876543210'
name: String
description: String
I want to use FTS on this to search without worrying about diacritical marks, how ever i want to let user select also by typing part of object ID(ex. last 4 char)
I got select like
`SELECT * FROM tabel LEFT JOIN tabel_fts on tabel_fts.domainObjectId = tabel.domainObjectId WHERE tabel_fts MATCH '3210*' OR tabel.domainObjectId LIKE '%3210%'
But in return i get error
unable to use function MATCH in the requested context (code 1 SQLITE_ERROR);
Is this possible to add additional condition to select with MATCH?

Try to remove "MATCH" into separate "SELECT":
`SELECT * FROM tabel LEFT JOIN (select * from tabel_fts WHERE tabel_fts.domainObjectId MATCH '3210*') as tabel_fts WHERE tabel.domainObjectId LIKE '%3210%' OR table_fts.ID IS NOT NULL
By the way:
In your "WHERE tabel_fts" it seemed you've missed a column name
There is no "ON" condition in tables JOINm just "WHERE". That's OK? May be it would be better to use UNION?

Get Wordpress posts with images link

I want to get wordpress posts with specific category and link of images.
As you know images links save to database in guid column, when post_type = attachment.
and ID of post and post_parent are the same.
Now I want to get posts and join guid column to same ID.
When I added Inner join to combine attachment and post, I got error!
Please help me, if you know the way that I can get post with specific category and images link of each post.
Here is my code:
SELECT
*
FROM
wp_posts p,
wp_postmeta m,
wp_terms t,
wp_term_taxonomy tt,
wp_term_relationships tr,
wp_terms t2,
wp_term_taxonomy tt2,
wp_term_relationships tr2
LEFT JOIN wp_posts AS p2
ON
p.ID = p2.post_parent
WHERE
p.post_type = 'post' AND p.post_status = 'publish'
AND p.ID = tr.object_id
AND t.term_id = tt.term_id
AND tr.term_taxonomy_id = tt.term_taxonomy_id
AND tt.taxonomy = 'category'
AND tt.term_id = t.term_id
AND t.name = 'Fashion'
GROUP BY
p.ID
ORDER BY
id
DESC
MySQL said:
#1054 - Unknown column 'p.ID' in 'on clause'

I suspect that the problem is due to mixing the old school comma syntax with the newer JOIN keyword.
Relevant excerpt from MySQL Reference Manual:
INNER JOIN and , (comma) are semantically equivalent in the absence of a join condition: both produce a Cartesian product between the specified tables (that is, each and every row in the first table is joined to each and every row in the second table).
However, the precedence of the comma operator is less than that of INNER JOIN, CROSS JOIN, LEFT JOIN, and so on. If you mix comma joins with the other join types when there is a join condition, an error of the form Unknown column 'col_name' in 'on clause' may occur. Information about dealing with this problem is given later in this section.
The easiest way to avoid this problem is to ditch the old school syntax for the join operation, use the JOIN keyword instead.
(It's great that the comma syntax is still valid, to provide backwards compatibility with existing SQL. But there's no good reason new development should use the comma syntax.)
Aside from that, there's a couple of big rock issues that stick out to me.
Seems like there's a lot of join conditions missing
Using * for the SELECT list in development can be useful shortcut, but we usually list the expressions we need to return, especially if we want to return id column from multiple tables, where we like to assign a column alias to avid duplicate columns names.
Relying on the non-standard extension to GROUP BY (when only_full_group_by is omitted from sql_mode to return values from "some" row in the collapsed group
Those all look like serious problems to me.
We can re-write the OP query to use JOIN keyword in place of comma syntax, and relocating conditions to the ON clause, this highlights what looks like missing join conditions:
SELECT *
FROM wp_posts p
JOIN wp_postmeta m
-- ON ???
JOIN wp_terms t
ON t.name = 'Fashion'
JOIN wp_term_taxonomy tt
ON tt.term_id = t.term_id
AND tt.taxonomy = 'category'
JOIN wp_term_relationships tr
ON tr.object_id = p.id
AND tr.term_taxonomy_id = tt.term_taxonomy_id
JOIN wp_terms t2
-- ON ???
JOIN wp_term_taxonomy tt2
-- ON ???
JOIN wp_term_relationships tr2
-- ON ??
LEFT
JOIN wp_posts AS p2
ON p2.post_parent = p.id
WHERE p.post_type = 'post'
AND p.post_status = 'publish'
GROUP
BY p.id
ORDER
BY p.id DESC
Where we are going to omit any join condition, and just match all rows to all other rows, then my preference is to include the (optional) CROSS keyword, as an aid the future reader, to signal that the omission of a join condition is by design, and not an oversight.

SQLite same column name on join

Using sqlite on android studio, I have two related tables "A" and "B", that both have a column "id". When I make a join on Android Studio, and try to get the value from "id" I get "B.id" whether I put
cursor.getInt(cursor.getColumnIndex("A.id")); // or
cursor.getInt(cursor.getColumnIndex("id"));
I'm considering changing the name of the columns so I can distinguish them easily, but I've seen that sqlite doesn't have any simple thing like "Alter Table "A" rename column", but I would have to duplicate the table with the correct name and deleting the old one so I'm trying to avoid this solution.
Also a solution I thought is to duplicate the column in the query putting something like "Select A.id, * from...", but is something I'd rather avoid.
Any idea why the code I posted might not work? Thanks

Define an alias on the columns, optionally selecting all other columns with *. These are not mutually exclusive, so the following will work:
SELECT a.id AS a_id, b.id AS b_id, * FROM ...
It will return the aliased columns along with all others, even if the data is redundant:
Columns: a_id, b_id, id, ..., id, ...
Frankly, you can't avoid all solutions. The two solutions that you already listed are about all you have to choose from. Sqlite does not automatically prefix table names to the column names, so there are really no other options.

With a Cursor you can (albeit it not recommended) use specific offsets (what the getColumnIndex method does is return the offset, the get???? methods all take on offset).
So say the query was SELECT * FROM A JOIN B ON A.id = B.maptoAid and
Table A has columns:-
id (offset 0) and
name (offset 1)
and Table B has columns:-
id and (offset 2)
maptoAid (offset 3) and
blah (offset 4)
Then (for the above only, the offsets have to be determined)
to get A.id use cursor.getInt(0);
to get B.id use cursor.getInt(2);
Note The use of offsets is discouraged far better to use column aliases (AS) along with the Cursor getColumnIndex method.
offsets are not tolerant of changes to the query, that is change the number or order of columns and offsets may have to be re-calculated.
names, via the getColumnIndex method (unless duplicating the same name) are tolerant of such changes
Such as
SELECT a.id AS aid, b.id AS bid .... other columns (aliased or not) .... FROM A JOIN B ON A.id = B.maptoAid
Or easier to code bit with greater overheads
SELECT *, A.id AS aid, B.id FROM A JOIN B ON A.id = B.maptoAid
and then use :-
cursor.getInt(cursor.getColumnIndex("aid"));
cursor.getInt(cursor.getColumnIndex("bid"));
I get "B.id" whether I put ...
and
Any idea why the code I posted might not work?
The reason why you get B.id is that the getColumnindex method doesn't finish looping when it finds the column BUT continues the loop, thus returning the last if there are more than one columns with the same name.
Also note (unless fixed) that the Cursor getColumnIndex method is also case sensitive. So cursor.getInt(cursor.getColumnIndex("Aid")) would return -1.

Combine MATCH with OR clause in the WHERE statement

I want to perform a query in which the WHERE clausule has the following condition:
one MATCH condition over a column in a FTS3 table
OR
another not MATCH condition over a column in a non FTS table.
Example:
Say that I have two tables
books_fts, which is a table with a content column for full text search.
books_tags, which is non FTS table with tags.
I want to search all the books that either contain 'Dikjstra' in their content or are tagged with the 'algorithm' word. So I run this query:
SELECT * from books_fts
LEFT OUTER JOIN books_tags ON books_fts.fk_id = books_tags.id
WHERE (books_fts MATCH 'content:%Dijkstra*')
OR (books_tags.tag = 'algorithm')
I think the query is right, and if I run it with either one of the OR clausules, it works.
However, when running it with the two clausules I get the following error:
unable to use function MATCH in the requested context
Seems to me that I cannot combine a MATCH with a non MATCH in the WHERE clause, even if each of them apply to different tables (one FTS and another non FTS).
Is this true? I cannot find information on it.
NOTE: if the causules are separated with AND instead of OR the query is valid.
Thanks.

It seems it's a known issue in SQL:
http://sqlite.1065341.n5.nabble.com/FTS3-bug-with-MATCH-plus-OR-td50714.html

How do I combine two queries into one?

This is for Android SQLite. I have two queries like this:
select * from table where name='name';
and
select * from table where name!='name' order by name;
I want to create a statement which combines these two queries. I tried union all but I can't do order by one statement and then combine. I tried this:
select * from table where name='name'
union all
select * from table where name!='name' order by name;
All it did is to combine the queries and then order by name. I don't want that. I want to do order by on the second statement first and then combine them.
To put the question differently, here is my data:
Name
a
b
c
d
e
f
g
h
i
j
But I want the output to be:
Name
g
a
b
c
d
e
f
h
i
j
I want to get one row to the top and then order the rest of the rows. Any help is appreciated.

No need to use temporary tables, you need to add an additional column to sort on. Something like this:
select 1, * from table where name='name'
union all
select 2, * from table where name!='name'
order by 1, name;
I don't have a sqlite install right now, but this trick should work. (you may have to add an alias to the first column).

Unless there is some other attribute of the table you can use to provide sorting that allows a join between the two selects as in How to combine two sql queries? then I think you'll have to store the result of the query that should float to the top in a temporary table and then add the sorted results to that table before storing it.
I've never used temporary tables in Android so can't provide an example but as far as I'm aware it's possible.
I'd recommend running the two queries separately and then combining the results in code if that's possible in your situation.

According to the SQLLite docs this cannot be done with a UNION or UNION ALL because those operations must be performed on a simple select, (ones without Order by).
http://www.sqlite.org/lang_select.html
There's probably a very clever way to do this that I don't know, which generally leads me to just do two queries and combine the results in java.
[EDIT] And Jhovanny has the very clever way to do it.

Can't test it right now, but something like this should work:
select t.*, case when name = 'name' then 0 else 1 as o from table t order by o, name;
Then you don't have the two selects nor the union. Assuming you can use a case statement in sqlite on android.