SQL Server's medium -efficient rotation conversionQuestion
It may be a performance challenge in SQL Server, especially when dealing with large datasets. This article discusses various methods for optimizing row conversion conversion.
Pivot function
Pivot function is a common choice for this task. Although it is not always the fastest way, it provides a direct and flexible way of conversion:
The polymer function and case expression
SELECT FirstName, Amount, PostalCode, LastName, AccountNumber FROM ( SELECT value, columnName FROM yourTable ) d PIVOT ( MAX(value) FOR columnName IN (FirstName, Amount, PostalCode, LastName, AccountNumber) ) piv;Pivot's replacement method is to use the polymer function and case expression:Multiple connections
In the case of PIVOT or polymerization function, multiple connections can be used:
SELECT MAX(CASE WHEN columnName = 'FirstName' THEN value END) Firstname, MAX(CASE WHEN columnName = 'Amount' THEN value END) Amount, MAX(CASE WHEN columnName = 'PostalCode' THEN value END) PostalCode, MAX(CASE WHEN columnName = 'LastName' THEN value END) LastName, MAX(CASE WHEN columnName = 'AccountNumber' THEN value END) AccountNumber FROM yourTable;dynamic pivot
For the unknown case that needs to be converted, you can use a dynamic SQL to build a PIVOT statement:
SELECT fn.value AS FirstName, a.value AS Amount, pc.value AS PostalCode, ln.value AS LastName, an.value AS AccountNumber FROM yourTable fn LEFT JOIN yourTable a ON fn.someCol = a.someCol AND a.columnName = 'Amount' LEFT JOIN yourTable pc ON fn.someCol = pc.someCol AND pc.columnName = 'PostalCode' LEFT JOIN yourTable ln ON fn.someCol = ln.someCol AND ln.columnName = 'LastName' LEFT JOIN yourTable an ON fn.someCol = an.someCol AND an.columnName = 'AccountNumber' WHERE fn.columnName = 'Firstname';
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