Fatal error encountered during command execution c# MySQL to DataGrid(wpf)

Fatal error encountered during command execution c# MySQL to DataGrid(wpf)

string query = "SELECT
q1.date,q1.Item,`openingstock`.openingstock,q1.Purchase,q1.Issue,
q1.Billno,sum(`openingstock`.openingstock+IFNULL(q1.Purchase,0)-IFNULL(q1.Issue,0))
as closingstock ,q1.Particulars, q1.Price FROM (SELECT DATE, Item, MAX(
CASE WHEN TYPE =1 THEN amount END ) Purchase, MAX( CASE WHEN TYPE =2 THEN
amount END ) Issue, Billno, Particulars, Price FROM ( SELECT 1 TYPE ,
DATE, Item, Billno, Particulars, Price, Quantity amount, @n := IF( @g =
DATE, @n +1, 1 ) rnum, @g := DATE FROM purchese CROSS JOIN ( SELECT @n
:=0, @g := NULL)i1 UNION ALL SELECT 2 , DATE, Item, Quantity amount,
Issueto, Issueto s, Issueto ss, @m := IF( @f = DATE, @m +1, 1 ) rnum, @f
:= DATE FROM issue CROSS JOIN (SELECT @m :=0, @f := NULL)i2)q GROUP BY
DATE, rnum )q1 INNER JOIN `openingstock` ON q1.Item =
`openingstock`.Item AND q1.date = `openingstock`.date ";
report.DataContext = MySQLSelectAda(query);
i get the error Fatal error encountered during command execution