I want to get all the rows that are the prefix of 'abcd' in mysql.
This query will get the job done, but it will not using the index of field1.
select field1
from table1
where 'abcd' LIKE CONCAT(field1, '%')
PS: this query will get field1='a' field1='ab' field1='abc'
Is there a way to get the same query result and use the index?
I assume you don't want field1='' to match?
Here's a way to get the index to be somewhat useful:
WHERE field1 BETWEEN 'a' AND 'abcd'
AND 'abcd' LIKE 'field1%'
To be slightly more maintainable, given that #x is 'abcd':
WHERE field1 BETWEEN LEFT(#x, 1) AND #x
AND #x LIKE CONCAT(field1, '%')
It may be that #variables won't work; in that case, conspire to use a JOIN:
SELECT a.field1
FROM ( SELECT 'abcd' AS x ) init
JOIN table1
WHERE field1 BETWEEN LEFT(init.x, 1) AND init.x
AND init.x LIKE CONCAT(field1, '%')
(and that may not be good enough)
A third approach would be to use a Stored Procedure to construct my WHERE suggestion with literals, then execute it.
Related
(MySQL)
I have a query to check if 'phone_number' or 'fax_number' startsWith a value from a given array,
lets say const possibleValues = [123,432,645,234]
currently my query runs with the 'or' condition, to check if -
'phone_number' or 'fax_number' that starts with 123
or
'phone_number' or 'fax_number' that starts with 432
or
'phone_number' or 'fax_number' that starts with 645
or
'phone_number' or 'fax_number' that starts with 234
it runs extremely slow on a big database, and I wish to make it faster,
is there a way to make it run faster?
I'm kinda new to sql queries,
any help would be highly appreciated!
You can try something like:
SELECT * FROM table_1
WHERE CONCAT(',', `phone_number`, ',') REGEXP ',(123|432|645|234),'
OR CONCAT(',', `fax_number`, ',') REGEXP ',(123|432|645|234),';
Demo
Try creating an in-line table and join with it.
WITH telnostart(telnostart) AS (
SELECT '123'
UNION ALL SELECT '432'
UNION ALL SELECT '645'
UNION ALL SELECT '234'
)
SELECT
*
FROM your_search_table
JOIN telnostart ON (
LEFT(tel_number,3) = telnostart
OR LEFT(fax_number,3) = telnostart
you can use a case statement to add a flag column
select *
,case when left(phone_number,3) in (123,432,645,234) or left(fax_number,3) in (123,432,645,234) then 1 else 0 end as contact_check_flag
from table_name
As per your requirement, you can filter it or use it elsewhere.
SELECT * FROM table_1
WHERE `phone_number` REGEXP '^(123|432|645|234)'
OR `fax_number` REGEXP '^(123|432|645|234)';
But it won't be fast. (And no regular INDEX will help.)
If there phone numbers are spelled out like in the US: "123-456-7890", then you could use a FULLTEXT(phone_number, fax_number) index and
SELECT * FROM table_1
WHERE MATCH(phone_number, fax_number)
AGAINST('123 432 645 234');
This is likely to be much faster, but not as "general".
I would like to search one value in multiple columns of my table.
Im making
SELECT* FROM myTableName WHERE'value' IN(column1, column2, column3);
This is working for me, but i wan't to make it with LIKE. Something like this:
SELECT* FROM myTableName LIKE '%value%' IN(column1, column2, column3);
Because i'm making a browser, so i need to use the LIKE.
I'm getting error and i don´t know how can i make it well.
Anyone knows something?
With PostgreSQL there is the ANY or ALL form:
WHERE col LIKE ANY( subselect )
or
WHERE col LIKE ALL( subselect )
where the subselect returns exactly one column of data.
You can try to use OR with LIKE instead of IN with LIKE
SELECT *
FROM myTableName
WHERE
column1 LIKE '%value%'
OR
column2 LIKE '%value%'
OR
column3 LIKE '%value%'
NOTE:
I will store column1,column2,column3 in one column if you need to search it because one column with only one LIKE will be higher performance than you used multiple columns.
select #q := concat('select * from Table1 ',
'where concat(', group_concat(column_name), ', "") like ?'
)
from information_schema.columns c
where table_name = 'Table1';
set #p = '%augusto%';
prepare st from #q;
execute st using #p;
deallocate prepare st;
Ref:Mysql query search a string in all columns of a table
You can use three like patterns with or:
WHERE column1 LIKE '%value%' OR
column2 LIKE '%value%' OR
column3 LIKE '%value%'
However, that is cumbersome because you have to repeat the pattern multiple times. There is a work-around that works in more recent versions of MySQL:
where exists (select 1
from (select t.column1 as val union all
select t.column2 as val union all
select t.column3 as val
) x
where x.val like '%value%'
)
This does not work in older versions of MySQL because the double nested correlation is not supported.
(Here is an example.)
I am trying to optimize the search engine of my wensite. My data base contains phrases. #word is defined as varchar and contains a similar phrase to the one which exist in the DB.
I want if the given search phrase matches exactly to the entry in DB the entry will be chosen, if nothing could be found, search with like '%phrase%' and if nothing will be find with this method, then the MATCH columnx against (phrase) method should be used. This is the code I tried with:
select distinct columnx
from tabley
where
( CASE when columnx LIKE #word is not null
then columnx LIKE #word
when columnx like concat('%',#word,'%') is not null
then columnx like concat('%',#word,'%')
else MATCH (columnx) AGAINST (#word) END
);
To make sure if the cases on a standalone select query works fine I used them separately in where clause. I get result for these queries:
select distinct columnx from view_materialisiert where MATCH (columnx) AGAINST (#word);
and
select distinct columnx from view_materialisiert where columnx like concat('%',#word,'%');
And as expected no result for:
select distinct columnx from view_materialisiert where columnx like #word;
The question is why i dont get any result when I use the case condition at all?
If you want values that match on any of the three condition, you can use boolean logic:
select columnx
from tabley
where columnx = #word
or columnx like concat('%', #word, '%')
or match(columnx) against (#word)
Or you can extend the case logic:
where case
when columnx = #word then 1
when columnx like concat('%', #word, '%') then 1
when match(columnx) against (#word) then 1
end
However I am unsure that's really what you expect. It seems like you want to iteratively check the conditions, trying the next one only when the preceding had no match on the entire table. This type of logic would be typically implemented with union all and not exists:
select columnx
from tabley
where columnx = #word
union all
select columnx
from tabley
where columnx like concat('%', #word, '%')
and not exists (select 1 from tabley where columnx = #word)
union all
select columnx
from tabley
where match(columnx) against (#word)
and not exists (select 1 from tabley where columnx = #word)
and not exists (select 1 from tabley where columnx like concat('%', #word, '%'))
How the database will optimize such query is highly dependent on your data and other factors. In the best case scenario, the following members will be "skipped" as soon as one member returns anything (because the not exists subquery is quite explicit about that), but there is no guarantee. You would need to assess the performance on your actual dataset.
Do only
MATCH (columnx) AGAINST ("+word" IN BOOLEAN MODE)
It is very fast. That expression eliminates the need for the exact match and some of the other cases.
The OR approaches mentioned are quite inefficient. They will check every row, usually with every test.
Caveats:
"Short" words cannot be used.
"Stop" words cannot be used.
If you aren't careful about those limitations, you will get nothing or everything. So do some preprocessing to decide when MATCH will work.
I have a query that looks at partial matches within two mysql tables to make a join:
SELECT table1.column, table2.column FROM table1, table2 WHERE table1.val LIKE table2.val
This works fine as a join, but... some of the values in table2 are actually substrings of the values in table one—specifically they're urls. So, table1.val might equal http://google.com while table2.val = google.com.
How do I use the '%' operator around the table2 val to make this comparison.
Thanks in advance!
Like this:
... WHERE table1.val LIKE CONCAT('%', table2.val, '%')
Note that this will not perform as well as table1.val = table2.val, as it must now search all rows in table2.
Q: How do I use the '%' operator around the table2 val to make this
comparison.
A: You don't :)
You can specify a column by name (e.g. "mycolumn"), by fully qualified name (e.g. "mytable.myname") or by ordinal (e.g. "1").
I have the following problem with a MySQL query in C#:
Given a list of strings, I want to query the database for any rows that match said strings. The strings are unique in that each string matches no more than one row. Today, my query looks something like this:
SELECT Id FROM SomeTable
WHERE SomeColumn IN("foo", "bar", "baz")
Now, ideally I would like to be able to map the result from the query directly to the list of strings I supplied in the IN clause:
String Returned ID
------------------------------------------
foo 123
bar NULL <-- Missing row filled with NULL
baz 42
This works fine as long as all strings I pass to the query match a row. When one is missing, however, I would like to fill in the blank with a NULL as in the example above.
Is there any way to accomplish this?
Edit: I should probably have pointed out that the solution must scale to a lot of strings. The way I do it right now is that I pass 100 at a time through the IN clause.
You could do this:
SELECT
helper.SomeColumn,
SomeTable.Id
FROM
(
SELECT 'foo' AS SomeColumn
UNION SELECT 'bar'
UNION SELECT 'baz'
) AS helper
LEFT JOIN SomeTable ON SomeTable.SomeColumn = helper.SomeColumn
Of course you can create the helper table (as a temp table) beforehand instead of inline.
Anyway, maybe it is smarter and more efficient to just do the query you have (WHERE SomeColumn IN (...)) and simply figure out the missing rows in your application. You will loop over them anyway, so you will notice.
What you could do is SELECT the set of strings as a result set and then LEFT JOIN on SomeTable.SomeColumn.
Try this:
SELECT Id
FROM (
SELECT "foo" SomeColumn
UNION ALL
SELECT "bar" AS SomeColumn
UNION ALL
SELECT "baz" AS SomeColumn
) b
LEFT JOIN
SomeTable a
ON a.SomeColumn = b.SomeColumn