I need to make a select like,
Select * from table WHERE column = x if column != -1
but i have no idea for now.
Anyone know or made in past something like that?
Thanks.
You should also write like this,
Select * from table
WHERE
1 = case when column != -1 then
case when column = x then 1 else 0 end
else 1 end
You can utilize case when in where clause.
Similarly you can add more conditional criteria like,
Select * from table
WHERE
1 = case when column != -1 then
case when column = x then 1 else 0 end
else 1 end
AND
1 = case when column1 [conditional operator] value then
case when column1 = xx then 1 else 0 end
else 1 end
This is just an example how you can integrate more conditional criteria together, even though you can add more case when in else part even.
Related
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Possible Duplicate:
Referring to a Column Alias in a WHERE Clause
SELECT
Trade.TradeId,
Isnull(Securities.SecurityType,'Other') SecurityType,
TableName,
CASE
WHEN
SecurityTrade.SecurityId IS NOT NULL
THEN
SecurityTrade.SecurityId
ELSE
Trade.SecurityId
END AS PricingSecurityID,
sum(Trade.Quantity)OVER(Partition by Securities.SecurityType, SecurityTrade.SecurityId,Trade.Price, Buy,Long ) as sumQuantity,
--added porfolio id for Getsumofqantity
Trade.PortfolioId,
Trade.Price,
case
when (Buy = 1 and Long = 1) then 1
when (Buy = 0 and Long = 0) then 1
else 0
end Position
from
Fireball_Reporting..Trade
where porfolioid =5 and Position =1
i want to use Position =1 in my where clause which is an alias of case
case
when (Buy = 1 and Long = 1) then 1
when (Buy = 0 and Long = 0) then 1
else 0
end Position
How can I use it in where clause?
I tried zo directly use that CASE statement in where clause, but failed.
WHERE Trade.SecurityId = #SecurityId AND PortfolioId = #GHPortfolioID AND
(case when (Buy = 1 and Long = 1) then 1 when (Buy = 0 and Long = 0) then 1 else 0 end Position = 1)
The SQL-Server docs says:
column_alias can be used in an ORDER BY clause, but it cannot be used in a WHERE, GROUP BY, or HAVING clause.
Similar in the MySQL doc it says:
Standard SQL disallows references to column aliases in a WHERE clause. This restriction is imposed because when the WHERE clause is evaluated, the column value may not yet have been determined.
In MySQL you can at least reuse aliases in the SELECT clause
You can't, not directly.
If you wrap the whole query in a sub-query, however, it works fine.
SELECT
*
FROM
(
SELECT
Trade.TradeId,
Isnull(Securities.SecurityType,'Other') SecurityType,
TableName,
CASE
WHEN SecurityTrade.SecurityId IS NOT NULL THEN SecurityTrade.SecurityId
ELSE Trade.SecurityId
END AS PricingSecurityID,
sum(Trade.Quantity)OVER(Partition by Securities.SecurityType,
SecurityTrade.SecurityId,Trade.Price, Buy,Long ) as sumQuantity,
--added porfolio id for Getsumofqantity
Trade.PortfolioId,
Trade.Price,
case
when (Buy = 1 and Long = 1) then 1
when (Buy = 0 and Long = 0) then 1
else 0
end Position
from
Fireball_Reporting..Trade
where
porfolioid = 5
)
AS data
WHERE
Position = 1
This means that you don't need to repeat the CASE statement in WHERE clause. (Maintainable and DRY).
It is also a structure that allows the optimiser to behave as if you had simply repeated yourself in the WHERE clause.
It's also very portable to other RDBMSs.
In SQL Server, then you also have another option...
SELECT
Trade.TradeId,
Isnull(Securities.SecurityType,'Other') SecurityType,
TableName,
CASE
WHEN SecurityTrade.SecurityId IS NOT NULL THEN SecurityTrade.SecurityId
ELSE Trade.SecurityId
END AS PricingSecurityID,
sum(Trade.Quantity)OVER(Partition by Securities.SecurityType,
SecurityTrade.SecurityId,Trade.Price, Buy,Long ) as sumQuantity,
--added porfolio id for Getsumofqantity
Trade.PortfolioId,
Trade.Price,
position.val AS Position
from
Fireball_Reporting..Trade
CROSS APPLY
(
SELECT
case
when (Buy = 1 and Long = 1) then 1
when (Buy = 0 and Long = 0) then 1
else 0
end AS val
)
AS position
where
porfolioid = 5
AND position.val = 1
You can't directly do this...but you can wrap an additional select around it all and use the where clause:
select * from
( SELECT
Trade.TradeId,
Isnull(Securities.SecurityType,'Other') SecurityType,
TableName,
CASE
WHEN
SecurityTrade.SecurityId IS NOT NULL
THEN
SecurityTrade.SecurityId
ELSE
Trade.SecurityId
END AS PricingSecurityID,
sum(Trade.Quantity)OVER(Partition by Securities.SecurityType, SecurityTrade.SecurityId,Trade.Price, Buy,Long ) as sumQuantity,
--added porfolio id for Getsumofqantity
Trade.PortfolioId,
Trade.Price,
case
when (Buy = 1 and Long = 1) then 1
when (Buy = 0 and Long = 0) then 1
else 0
end Position
from
Fireball_Reporting..Trade
where porfolioid =5 and Position =1
)x
where x.position = 1
I'm probably missing something but surely this will cover it:
WHERE (Buy = 1 and Long = 1) OR (Buy = 0 and Long = 0)
I would like to do the following.
Update a field based on the value of another field like
update table set if(fielda=1){fieldb=2 fieldc=3}else{fieldd=2 fielde=3}
I know this is not valid mysql but its the best way for me to describe the problem.
update table set
b = case when a = 1 then 2 else b end,
c = case when a = 1 then 3 else c end,
d = case when a = 1 then d else 2 end,
e = case when a = 1 then e else 3 end
edit
according to your comment try this:
update table set
datefield_a = case when field_a = 1 then now() else datefield_a end,
datefield_b = case when field_a <> 1 then now() else datefield_b end
I think this syntax will achieve the result you attempted to specify.
UPDATE mytable
SET fieldb = CASE WHEN fielda = 1 THEN 2 ELSE fieldb END
, fieldc = CASE WHEN fielda = 1 THEN 3 ELSE fieldc END
, fieldd = CASE WHEN fielda = 1 THEN fieldd ELSE 2 END
, fielde = CASE WHEN fielda = 1 THEN fielde ELSE 3 END
The "trick" here is that we are updating all four columns, but in some "cases", we are assigning the current value of the column back to the column, resulting in no real change to the column value. (Once you get your mind bent around that idea, it's pretty easy.)
With MySQL, we do have a handy IF function (not available in most other RDBMS) that we can use to abbreviate that a bit, and achieve the same thing:
UPDATE mytable
SET fieldb = IF(fielda = 1, 2, fieldb)
, fieldc = IF(fielda = 1, 3, fieldc)
, fieldd = IF(fielda = 1, fieldd, 2)
, fielde = IF(fielda = 1, fielde, 3)
The pain is that you still have to repeat that same conditional test multiple times.
A single scan through the table (like these statements do), and getting all those assignments done in one fell swoop is going to be faster (and more efficient) than breaking this up and doing the assignments piecemeal using multiple statements.
I'm about to build some sort of function or query where I can check if a certain record already exists in the database. The following rules apply:
The table has 6 columns
My yet-to-build-query has access to a complete row-object (all 6 values)
This query should find each row with at least 4 out of 6 corresponding values from the object I passed
Using MySQL
Is it even possible to build a query like this? My goal is to have a function which can return true if it's likely that a row like the passed object is already existing in the database.
Is my only option to make a query with multiple where-statements (where I try for each combination 4 different values)?
pseudo:
function getSimilarRow(Row_Object $row)
{
//select *
//from table_x
//where 4 out of 6 properties from object $row apply
}
You could use a case statement in the where clause for each property you are trying to match. If it meets the criteria then give the case statement a value of 1; if it doesn't then give it 0. The sum of the cases should then be >= 4.
I'm not that familiar with MySQL but the following will work (I knocked up a quick SQL Fiddle to show it working):
select * from SomeTable where
(case when propertyOne = 'value1' then 1 else 0 end) +
(case when propertyTwo = 'value2' then 1 else 0 end) +
(case when propertyThree = 'value3' then 1 else 0 end) +
(case when propertyFour = 'value4' then 1 else 0 end) +
(case when propertyFive = 'value5' then 1 else 0 end) +
(case when propertySix = 'value6' then 1 else 0 end) >= 4
Obviously you could change your logic in each clause if you'd prefer them to be likes or anything. You could even apply a weighting to each column by using something other than just 1 if you needed to get really creative.
seems like a stupid question...
I have a mysql table where I want to modify column A to a number 0 or 1 depending on the condition of another column B
So: if( B > 500 ) A = 1 ELSE A = 0
Column A = INT
Column B = DOUBLE
How do you do something like this in sql?
Thanks,
Erik
Try the following statement,
UPDATE tableName
SET A = (B > 500)
SQLFiddle Demo
(B > 500) is a boolean arithmetic in mysql which returns 1 and 0 for true and false , respectively.
You can also use CASE for much more RDBMS friendly,
UPDATE tableName
SET A = CASE WHEN B > 500 THEN 1 ELSE 0 END
I would like to do the following.
Update a field based on the value of another field like
update table set if(fielda=1){fieldb=2 fieldc=3}else{fieldd=2 fielde=3}
I know this is not valid mysql but its the best way for me to describe the problem.
update table set
b = case when a = 1 then 2 else b end,
c = case when a = 1 then 3 else c end,
d = case when a = 1 then d else 2 end,
e = case when a = 1 then e else 3 end
edit
according to your comment try this:
update table set
datefield_a = case when field_a = 1 then now() else datefield_a end,
datefield_b = case when field_a <> 1 then now() else datefield_b end
I think this syntax will achieve the result you attempted to specify.
UPDATE mytable
SET fieldb = CASE WHEN fielda = 1 THEN 2 ELSE fieldb END
, fieldc = CASE WHEN fielda = 1 THEN 3 ELSE fieldc END
, fieldd = CASE WHEN fielda = 1 THEN fieldd ELSE 2 END
, fielde = CASE WHEN fielda = 1 THEN fielde ELSE 3 END
The "trick" here is that we are updating all four columns, but in some "cases", we are assigning the current value of the column back to the column, resulting in no real change to the column value. (Once you get your mind bent around that idea, it's pretty easy.)
With MySQL, we do have a handy IF function (not available in most other RDBMS) that we can use to abbreviate that a bit, and achieve the same thing:
UPDATE mytable
SET fieldb = IF(fielda = 1, 2, fieldb)
, fieldc = IF(fielda = 1, 3, fieldc)
, fieldd = IF(fielda = 1, fieldd, 2)
, fielde = IF(fielda = 1, fielde, 3)
The pain is that you still have to repeat that same conditional test multiple times.
A single scan through the table (like these statements do), and getting all those assignments done in one fell swoop is going to be faster (and more efficient) than breaking this up and doing the assignments piecemeal using multiple statements.