Who directed the episode that originally aired on March 18, 1988?
CREATE TABLE table_20967430_4 (directed_by VARCHAR, original_air_date VARCHAR)
SELECT directed_by FROM table_20967430_4 WHERE original_air_date = "March 18, 1988"
<s>[INST] Write mssql query to answer the following question given the database schema. Schema: CREATE TABLE table_20967430_4 (directed_by VARCHAR, original_air_date VARCHAR) Question: Who directed the episode that originally aired on March 18, 1988? [/INST] SELECT directed_by FROM table_20967430_4 WHERE original_air_date = "March 18, 1988" </s>