Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_15318324_1 (r_z___arcsecond__ VARCHAR, target_datum VARCHAR)
### Question:
How many values of r z(arcsecond) are associated with a target datum of Ireland 1965?
### Answer:
SELECT r_z___arcsecond__ FROM table_15318324_1 WHERE target_datum = "Ireland 1965"