Convert Rows To Columns Using Dynamic Pivot In SQL Server

Article

In this article, we will show how to convert rows to columns using Dynamic Pivot in SQL Server.

PIVOT rotates a table-valued expression by turning the unique values from one column in the expression into multiple columns in the output and performs aggregations where they are required on any remaining column values that are wanted in the final output.

Scenario

We have decided to build a dynamic database by creating only three tables as shown below.

The “Tables” will be used to hold the table names like Users, Products….etc.

The “Fields” will be used to hold the fields name related to each table.

The “Field Value” will be used to hold the value of each field.

The available data

The desired data should look like

Steps

Get a list of the "Field Values" (Rows)

In this section, we will get a list of "Field Values" that should be shown as Rows by doing the following,

Create a table "dataquery" that will hold the field values data.

BEGIN try
DROP TABLE ##dataquery
END try
BEGIN catch
END catch
CREATE TABLE ##dataquery
(
id INT NOT NULL,
tablename VARCHAR(50) NOT NULL,
fieldname VARCHAR(50) NOT NULL,
fieldvalue VARCHAR(50) NOT NULL
);

Query the field values data filtered by "TableID" and insert the output into the created table in the above step.

INSERT INTO ##dataquery
SELECT Row_number()
OVER (
partition BY (fields.fieldname)
ORDER BY fieldvalue.fieldvalue) ID,
tables.tablename,
fields.fieldname,
fieldvalue.fieldvalue
FROM tables
INNER JOIN fields
ON tables.tid = fields.tid
INNER JOIN fieldvalue
ON fields.fid = fieldvalue.fid
WHERE tables.tid = @TableID

Output

Get a list of the "Fields" (Columns)

In this section, we will retrieve the list of the fields filtered by "TableID" by using the below SQL statement

DECLARE @DynamicColumns AS VARCHAR(max)
SELECT @DynamicColumns = COALESCE(@DynamicColumns + ', ', '')
+ Quotename(fieldname)
FROM (SELECT DISTINCT fieldname
FROM fields
WHERE fields.tid = @TableID) AS FieldList

COALESCE - Evaluates the arguments in order and returns the current value of the first expression that initially does not evaluate to NULL.
Quotename - Returns a Unicode string with the delimiters added to make the input string a valid SQL Server delimited identifier.

Build the Dynamic Pivot Table Query

In this section, we will combine the above two queries to build our Dynamic Pivot

DECLARE @FinalTableStruct AS NVARCHAR(max)
SET @FinalTableStruct = 'SELECT ' + @DynamicColumns +
' from ##DataQuery x pivot ( max( FieldValue ) for FieldName in (' + @DynamicColumns + ') ) p '
EXECUTE(@FinalTableStruct)