The title is a bit confusing, so I'll explain with an example what I'm trying to do.
I have a field called "modifier". This is a field with concatenated values for each individual. For example, the value in one row could be:
*26,50,4 *
and the value in the next row
*4 *
And the table (Table A) would look something like this:
Key Modifier
1 *26,50,4 *
2 *4 *
3 *1,2,3,4 *
The asterisks are always going to be in the same position (here, 1 and 26) with an uncertain number of numbers in between, separated by commas.
What I'd like to do is "join" this "modifier" field to another table (Table B) with a list of possible values for that modifier. e.g., that table could look like this:
ID MOD
1 26
2 3
3 50
4 78
If a value in A.modifier appears in B.mod, I want to keep that row in Table A. Otherwise, leave it out. (I use the term "join" loosely because I'm not sure that's what I need here.)
Is this possible? How would I do it?
Thanks in advance!
edit 1: I realize I can use regular expressions and do a bunch of or statements that search for the comma-separated values in the MOD list, but is there a better way?
One way to do it is using TRIM, string concatenations and LIKE.
SELECT *
FROM tableA a
WHERE EXISTS(
SELECT 1 FROM tableB b
WHERE
','|| trim( trim( BOTH '*' FROM a.Modifier )) ||','
LIKE '%,'|| b.mod || ',%'
);
Demo --> http://www.sqlfiddle.com/#!4/1caa8/10
This query migh be still slow for huge tables (it always performs full scans of tables or indexes), however it should be faster than using regular expressions or parsing comma separated lists into individual values.
Related
I would like to implement for 1 column multiple specific parameters like:
select * from table1
where column1 = a or column1 = b or column1 = c ...
Can it be done in a better way (the SQL Statement in Use is over 10 lines long with the OR statements it'll grow another 10 lines O.o and it'll make the code much slower!)
You can use in:
select t.*
from t
where column in ( . . . );
The in list is pretty equivalent to a bunch of or conditions. There are some nuances. For instance, all the values in the in list will be converted to the same type. If one is a number and the rest are strings, then all will be converted to strings -- perhaps generating an error.
For performance, you want an index on t(column).
I would like to ask if it is possible to do this:
For example the search string is '009' -> (consider the digits as string)
is it possible to have a query that will return any occurrences of this on the database not considering the order.
for this example it will return
'009'
'090'
'900'
given these exists on the database. thanks!!!!
Use the Like operator.
For Example :-
SELECT Marks FROM Report WHERE Marks LIKE '%009%' OR '%090%' OR '%900%'
Split the string into individual characters, select all rows containing the first character and put them in a temporary table, then select all rows from the temporary table that contain the second character and put these in a temporary table, then select all rows from that temporary table that contain the third character.
Of course, there are probably many ways to optimize this, but I see no reason why it would not be possible to make a query like that work.
It can not be achieved in a straight forward way as there is no sort() function for a particular value like there is lower(), upper() functions.
But there is some workarounds like -
Suppose you are running query for COL A, maintain another column SORTED_A where from application level you keep the sorted value of COL A
Then when you execute query - sort the searchToken and run select query with matching sorted searchToken with the SORTED_A column
Does SQLite offer a way to search every column of a table for a searchkey?
SELECT * FROM table WHERE id LIKE ...
Selects all rows where ... was found in the column id. But instead to only search in the column id, I want to search in every column if the searchstring was found. I believe this does not work:
SELECT * FROM table WHERE * LIKE ...
Is that possible? Or what would be the next easy way?
I use Python 3 to query the SQLite database. Should I go the route to search through the dictionary after the query was executed and data returned?
A simple trick you can do is:
SELECT *
FROM table
WHERE ((col1+col2+col3+col4) LIKE '%something%')
This will select the record if any of these 4 columns contain the word "something".
No; you would have to list or concatenate every column in the query, or reorganize your database so that you have fewer columns.
SQLite has full-text search tables where you can search all columns at once, but such tables do not work efficiently with any other queries.
I could not comment on #raging-bull answer. So I had to write a new one. My problem was, that I have columns with null values and got no results because the "search string" was null.
Using coalesce I could solve that problem. Here sqlite chooses the column content, or if it is null an empty string (""). So there is an actual search string available.
SELECT *
FROM table
WHERE (coalesce(col1,"") || coalesce(col2,"") || coalesce(col3,"") || coalesce(col4,"")) LIKE '%something%')
I'm not quite sure, if I understood your question.
If you want the whole row returned, when id=searchkey, then:
select * from table where id=searchkey;
If you want to have specific columns from the row with the correct searchkey:
select col1, col2, col3 from table where id=searchkey;
If you want to search multiple columns for the "id": First narrow down which columns this could be found in - you don't want to search the whole table! Then:
select * from table where col1=searchkey or col2=searchkey or col3=searchkey;
I have a table in Postgres. In that table more than 1000 names are there. Most of the names are start with SHRI or SMT. I want to delete this SHRT and SMT from the names and to save original name only. How can I do that with out any database function?
I'll step you through the logic:
Select left(name,3) from table
This select statement will bring back the first 3 chars of a column (the 'left' three). If we are looking for SMT in the first three chars, we can move it to the where statement
select * from table where left(name,3) = 'SMT'
Now from here you have a few choices that can be used. I'm going to keep to the left/right style, though replace could likely be used. We want the chars to the right of the SMT, but we don't know how long each string is to pick out those chars. So we use length() to determine that.
select right(name,length(name)-3) from table where left(name,3) = 'SMT'
I hope my syntax is right there, I'm lacking a postgres environment to test it. The logic is 'all the chars on the right of the string except the last 3 (the minus 3 excludes the 3 chars on the left. change this to 4 if you want all but the last 4 on the left)
You can then change this to an update statement (set name = right(name,length(name)-3) ) to update the table, or you can just use the select statement when you need the name without the SMT, but leave the SMT in the actual data.
I have a table A with this column:
IDS(VARCHAR)
1|56|23
I need to run this query:
select TEST from TEXTS where ID in ( select IDS from A where A.ID = xxx )
TEXTS.ID is an INTEGER. How can I split the string A.IDS into several ints for the join?
Must work on MySQL and Oracle. SQL99 preferred.
First of all, you should not store data like this in a column. You should split that out into a separate table, then you would have a normal join, and not this problem.
Having said that, what you have to do is the following:
Convert the number to a string
Pad it with the | (your separator) character, before it, and after it (I'll tell you why below)
Pad the text you're looking in with the same separator, before and after
Do a LIKE on it
This will run slow!
Here's the SQL that does what you want (assuming all the operators and functions work in your SQL dialect, you don't say what kind of database engine this is):
SELECT
TEXT -- assuming this was misspelt?
FROM
TEXTS -- and this as well?
JOIN A ON
'|' + A.IDS + '|' LIKE '%|' + CONVERT(TEXTS.ID) + '|%'
The reason why you need to pad the two with the separator before and after is this: what if you're looking for the number 5? You need to ensure it wouldn't accidentally fit the 56 number, just because it contained the digit.
Basically, we will do this:
... '|1|56|23|' LIKE '%|56|%'
If there is ever only going to be 1 row in A, it might run faster if you do this (but I am not sure, you would need to measure it):
SELECT
TEXT -- assuming this was misspelt?
FROM
TEXTS -- and this as well?
WHERE
(SELECT '|' + IDS + '|' FROM A) LIKE '%|' + CONVERT(TEXTS.ID) + '|%'
If there are many rows in your TEXTS table, it will be worth the effort to add code to generate the appropriate SQL by first retrieving the values from the A table, construct an appropriate SQL with IN and use that instead:
SELECT
TEXT -- assuming this was misspelt?
FROM
TEXTS -- and this as well?
WHERE
ID IN (1, 56, 23)
This will run much faster since now it can use an index on this query.
If you had A.ID as a column, and the values as separate rows, here's how you would do the query:
SELECT
TEXT -- assuming this was misspelt?
FROM
TEXTS -- and this as well?
INNER JOIN A ON TEXTS.ID = A.ID
This will run slightly slower than the previous one, but in the previous one you have overhead in having to first retrieve A.IDS, build the query, and risk producing a new execution plan that has to be compiled.