CREATE TABLE t1 (f1 double, f2 BIGINT);
INSERT INTO t1 SET f1 = -1.0e+30 ;
INSERT INTO t1 SET f1 = +1.0e+30 ;
SELECT f1 AS double_val, CAST(f1 AS   SIGNED INT) AS cast_val FROM t1;
double_val	cast_val
-1e+30	-9223372036854775808
1e+30	-9223372036854775808
SELECT -1.0e+30 AS double_val, CAST(-1.0E+30 AS   SIGNED INT) as cast_val;
double_val	cast_val
-1e+30	-9223372036854775807
SELECT +1.0e+30 AS double_val, CAST(+1.0E+30 AS   SIGNED INT) as cast_val;
double_val	cast_val
1e+30	9223372036854775807
UPDATE t1 SET f2 = f1;
Warnings:
Warning	1264	Data truncated; out of range for column 'f2' at row 1
Warning	1264	Data truncated; out of range for column 'f2' at row 2
SELECT f1 AS double_val, f2 AS impl_cast_val FROM t1;
double_val	impl_cast_val
-1e+30	-9223372036854775808
1e+30	9223372036854775807