return ct.LengthValue.Int64, true
	}
	return ct.SQLColumnType.Length()
}

// DecimalSize returns the scale and precision of a decimal type.
func (ct ColumnType) DecimalSize() (precision int64, scale int64, ok bool) {
	if ct.DecimalSizeValue.Valid {
		return ct.DecimalSizeValue.Int64, ct.ScaleValue.Int64, true
	}
	return ct.SQLColumnType.DecimalSize()
}

// Nullable reports whether the column may be null.

	ColumnType() (columnType string, ok bool) // varchar(64)
	PrimaryKey() (isPrimaryKey bool, ok bool)
	AutoIncrement() (isAutoIncrement bool, ok bool)
	Length() (length int64, ok bool)
	DecimalSize() (precision int64, scale int64, ok bool)
	Nullable() (nullable bool, ok bool)
	Unique() (unique bool, ok bool)
	ScanType() reflect.Type
	Comment() (value string, ok bool)
	DefaultValue() (value string, ok bool)
}

pkg database/sql/driver, type TxOptions struct, ReadOnly bool
pkg database/sql, func Named(string, interface{}) NamedArg
pkg database/sql, method (*ColumnType) DatabaseTypeName() string
pkg database/sql, method (*ColumnType) DecimalSize() (int64, int64, bool)
pkg database/sql, method (*ColumnType) Length() (int64, bool)
pkg database/sql, method (*ColumnType) Name() string
pkg database/sql, method (*ColumnType) Nullable() (bool, bool)

			}
		case "salary":
			if precision, o, _ := columnType.DecimalSize(); (fullSupported || precision != 0) && precision != 2 {
				t.Fatalf("salary's precision should be 2, but got %v %v", precision, o)
			}
		case "birthday":
			if precision, _, _ := columnType.DecimalSize(); (fullSupported || precision != 0) && precision != 2 {

		precision, scale, ok := columnType.DecimalSize()
		if ok {
			if !strings.HasPrefix(fullDataType, fmt.Sprintf("%s(%d,%d)", realDataType, precision, scale)) &&
				!strings.HasPrefix(fullDataType, fmt.Sprintf("%s(%d)", realDataType, precision)) {
				alterColumn = true
			}
		}
	} else {
		if precision, _, ok := columnType.DecimalSize(); ok && int64(field.Precision) != precision {