We use IN clause to replace many OR conditions.
Like, can I have any other clause to replace many AND condition?
That would not make sense:
YourColumn AND_IN (1,2,3)
This would never be true, since a column cannot be two values at once.
No,
Thats because one field won't be having multiple values.
for eg.
You would never write a query that says
SELECT *
FROM
tblName
WHERE
fldCol = 1
AND fldCol = 2
AND fldCol = 3;
I think you are looking for the alternative for this query,
SELECT ID
FROM TableName
WHERE col = 1 AND col = 2 AND col = 3
which will give empty result set because a record can have only one value at a time. This should be written as:
SELECT ID
FROM TableName
WHERE col IN (1, 2, 3)
GROUP BY ID
HAVING COUNT(*) = 3
SQL of Relational Division
Related
To get a record I normally use this kind of query:
select * from tablename where columnName = 'abc'
This query search for all abc in the table. However I want just to get only first record that has abc and don't look for other.
Please suggest me sql query for this purpose.
This will just return the first instance as it scans the table.
select * from tablename where columnName = 'abc' limit 1;
I need a query in which it starts off by selecting the entire table, then there would be a few more querys that would remove entries from the first query. Ive accomplished this by using several querys and then comparing the results in my application. I was wondering if I can accomplish this in a single query.
Algorithm
Select All AccountIDs from table
Select AccountIDs from table where parameter1 = true
Remove those matches from the original query result
Select AccountIDs from table where parameter2 = true
Remove those matches from the remaining query result
and so on up to N parameters.
This would need to also be compatible with both mySQL and SQLite
I think you are looking for this:
SELECT AccountID FROM the_table
LEFT JOIN (
SELECT AccountID FROM the_table
WHERE
parameter1 = true OR
... OR
parameterN = true ;
) AS not_included USING (AccountID)
WHERE not_included.AccountID IS NULL -- only items with no match in the "not_included" sub-query
The not_included subquery returns all items for which any parameter is set to TRUE. You actually want to exclude these records from your final result set.
Then LEFT-JOIN the_table (i.e. all items) to this sub-result. The WHERE...IS NULL clause excludes items present in the_table but not present in not_included.
Therefore only items which you do not want to exclude remain in the final result set.
The most direct way to implement your algorithm is to use a compound SELECT statement:
SELECT AccountID FROM MyTable
EXCEPT
SELECT AccountID FROM MyTable WHERE parameter1 = 1
EXCEPT
SELECT AccountID FROM MyTable WHERE parameter2 = 1
However, this is also possible with a single WHERE expression:
SELECT AccountID
FROM MyTable
WHERE NOT (parameter1 = 1 OR
parameter2 = 1 OR
...)
I have this kind of simple query that returns a not null integer field for a given id:
SELECT field1 FROM table WHERE id = 123 LIMIT 1;
The thing is if the id is not found, the resultset is empty. I need the query to always return a value, even if there is no result.
I have this thing working but I don't like it because it runs 2 times the same subquery:
SELECT IF(EXISTS(SELECT 1 FROM table WHERE id = 123) = 1, (SELECT field1 FROM table WHERE id = 123 LIMIT 1), 0);
It returns either field1 if the row exists, otherwise 0. Any way to improve that?
Thanks!
Edit following some comments and answers: yes it has to be in a single query statement and I can not use the count trick because I need to return only 1 value (FYI I run the query with the Java/Spring method SimpleJdbcTemplate.queryForLong()).
MySQL has a function to return a value if the result is null. You can use it on a whole query:
SELECT IFNULL( (SELECT field1 FROM table WHERE id = 123 LIMIT 1) ,'not found');
As you are looking for 1 record, (LIMIT 1) then this will work.
(SELECT field1 FROM table WHERE id = 123)
UNION
(SELECT 'default_value_if_no_record')
LIMIT 1;
Can be a handy way to display default values, or indicate no results found. I use it for reports.
See also http://blogs.uoregon.edu/developments/2011/03/31/add-a-header-row-to-mysql-query-results/ for a way to use this to create headers in reports.
You could include count(id). That will always return.
select count(field1), field1 from table where id = 123 limit 1;
http://sqlfiddle.com/#!2/64c76/4
You can use COALESCE
SELECT COALESCE(SUM(column),0)
FROM table
If someone is looking to use this to insert the result INTO a variable and then using it in a Stored Procedure; you can do it like this:
DECLARE date_created INT DEFAULT 1;
SELECT IFNULL((SELECT date FROM monthly_comission WHERE date = date_new_month LIMIT 1), 0)
INTO date_created
WHERE IFNULL((SELECT date FROM monthly_comission WHERE date = date_new_month LIMIT 1), 0) = 0;
With this you're storing in the variable 'date_created' 1 or 0 (if returned nothing).
Do search with LEFT OUTER JOIN. I don't know if MySQL allows inline VALUES in join clauses but you can have predefined table for this purposes.
k-a-f's answer works for selecting one column, if selecting multiple column, we can.
DECLARE a BIGINT DEFAULT 1;
DECLARE b BIGINT DEFAULT "name";
SELECT id, name from table into a,b;
Then we just need to check a,b for values.
if you want both always a return value but never a null value you can combine count with coalesce :
select count(field1), coalesce(field1,'any_other_default_value') from table;
that because count, will force mysql to always return a value (0 if there is no values to count) and coalesce will force mysql to always put a value that is not null
How can i run mysql and or query together instant of separate query.
e.g.:
And query:
select * form tablename where name='A' and password="A" and id='A';
Or query:
select * form tablename where name='A' or password="A" or id='A';
-These are 2 different query,can i make these query together?what is the syntax??
Use parentheses to group the conditions?
SELECT * FROM table WHERE (X and Y or Z) AND (P and Q or F)
Well, you can just union them but, since one is a subset of the other, it's not strictly necessary:
select * from tablename
where name = 'A' and password = 'A' and id = 'A'
union select * from tablename
where name = 'A' or password = 'A' or id = 'A'
That will give you exactly the same results as if you had just run the second query on its own. That will make sense once you realise that every single row from the first query has a name equal to 'A', so it will match the first part of the where clause in the second query.
If you want duplicate rows for those returned in both queries, just use union all instead of union.
If you were using 'A' as just a placeholder and its values are different in the two queries, then you have two approaches. Use a construct like:
... where (name = 'A' and password = 'B' and id = 'C')
or name = 'D' or password = 'E' or id = 'F'
or use the union solution I gave above, something like:
select * from tablename
where name = 'A' and password = 'B' and id = 'C'
union select * from tablename
where name = 'D' or password = 'E' or id = 'F'
(use union all when you know there is no possibility of duplicates between the two queries, - it will save the DBMS the trouble of removing non-existent duplicates - that's not the case with these queries).
The union may give better performance on a DBMS that can hive off the two selects more easily to separate query engines (something that would be more difficult with a single query with a complex where clause). Of course, as will all optimisations, measure, don't guess.
It is not clear what you expect as the result, but my guess is you want a UNION:
SELECT 1 `query`, `name`, `password`, `id`
FROM `tablename` WHERE `name`='A' and `password`='A' and `id`='A'
UNION
SELECT 2 `query`, `name`, `password`, `id`
FROM `tablename` WHERE `name`='A' or `password`='A' or `id`='A'
Note that the first column query in result is required to separate results from the two queries because union of (X and Y) and (X or Y) is always (X or Y).
Use () for such type of conditions
select * form tablename
where name='A' OR password="A" OR id='A' OR
(name='A' AND password="A" AND id='A')
If you want to check for same string as A here then you will get same o/p using following query
select * form tablename
where name='A' OR password="A" OR id='A'
Just combine the conditions with WHERE
SELECT * FROM tablename WHERE (name='A' AND password='A' AND id='A') OR name='A' OR password='A' OR id='A'
The parentheses ensure that the whole AND expressions "validates" only if ALL the containing conditions are true while the rest macthes the OR
So,
SELECT * FROM table WHERE col LIKE '%'
will return everything. Is there a wildcard for the query
SELECT * FROM table WHERE col = '*'
Clearly * doesn't work, I just put it there to indicate where I'd like a wildcard. The column I'm selecting from contains an integer between 1 and 12, and I want to be able to select either all records with a particular number, or all records with a wildcard.
Thanks,
LIKE is basically the same as =, except LIKE lets you use wildcards.
These two queries will return the same results:
SELECT * FROM table WHERE col LIKE 'xyz';
SELECT * FROM table WHERE col='xyz';
Without a '%' in the LIKE query, it is effectively the same as '='.
If you're doing a selection on an integer column, you should consider using the IN() or BETWEEN operators. It sounds like you have two separate conditions that should be handled in your code however, rather than in the query, as your conditions dictate that you need at least two different kinds of queries.
Edit: I should clarify that LIKE and = are similar only in normal, humdrum string comparison usage. You should check the MySQL Manual for specifics on how it works, as there are situations where it's not the same (such as language sets).
If you want to select everything, why are you attaching the WHERE clause at all? Just leave it off conditionally instead of putting a wildcard into it.
The reason for using LIKE is because the = does not offer wildcard support. Otherwise there would be no reason for LIKE
SELECT * FROM table WHERE col RLIKE '.*'
i.e. regular-expression LIKE.
zombat's answer is great, but I only noticed in his answer that you are selecting integers. He mentioned IN() and BETWEEN(). Here's examples using those syntaxes, as well as some other options you have for an integer field.
SELECT * FROM table WHERE col = 1;
SELECT * FROM table WHERE col BETWEEN 1 AND 12;
SELECT * FROM table WHERE col BETWEEN 6 AND 12;
SELECT * FROM table WHERE col <= 6;
SELECT * FROM table WHERE col < 6;
SELECT * FROM table WHERE col >= 6;
SELECT * FROM table WHERE col > 6;
SELECT * FROM table WHERE col <> 6;
SELECT * FROM table WHERE col IN (1,2,5,6,10);
SELECT * FROM table WHERE col NOT IN (1,2,5,6,10);
Assuming your query is parameter driven a case statement is probably appropriate
select * from mytable
where col like case when #myvariable is null then % else myvariable end
Where #myvariable is either null if you dont want a value otherwise it would use the integer value you pass in.
I have encountered such a case while building a stored procedure for a report
Following is my solution, hope this is what you had in mind :)
set #p = "ALL";
Query:
select * from fact_orders
where
dim_country_id = if(#p is null or #p="ALL", dim_country_id, #p)
limit 10
;
If your values are in the the range (1,12) then:
select * from table where col>=5 and col<=5; //this is equal to col=5
select * from table where col>=0 and col<=12; //this is equal to col=any value
The same line can produce both effects by choosing the 2 parameters appropriately.
I faced a similar problem when I needed a single prepared statement which should work with 2 different ways , either checking for a particular value in a column or ignoring that column completely.