SQL Server 2019

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select isnumeric('.')

(No column name)

1

select cast('.' as float)
Msg 8114 Level 16 State 5 Line 1
Error converting data type varchar to float.

select isnumeric('-')

(No column name)

1

select cast('-' as float)
Msg 8114 Level 16 State 5 Line 1
Error converting data type varchar to float.

select isnumeric('-.')

(No column name)

1

select cast('-.' as float)
Msg 8114 Level 16 State 5 Line 1
Error converting data type varchar to float.

select isnumeric('$1')

(No column name)

1

select cast('$1' as float)
Msg 8114 Level 16 State 5 Line 1
Error converting data type varchar to float.