CREATE TABLE table_19623 ("Explosion" CLOB, "Location" CLOB, "Date" CLOB, "Yield  ( approximate ) " CLOB, "Altitude  ( km ) " CLOB, "Nation of Origin" CLOB)

What was the yield of the K-4 explosion?
SELECT "Yield (approximate)" FROM table_19623 WHERE "Explosion" = 'K-4'
SELECT "Yield (approximate)" FROM "table_19623" WHERE "Explosion" = 'K-4'