SQL Server查詢-哪個性能更好？

Question

我認為查詢1比查詢2更易讀，但是我想知道它們之間在性能方面是否有任何區別？

查詢1

UPDATE table_1
SET col_1 = 
      CASE WHEN table_1.col_pk IS NULL THEN value1
           ELSE value2
      END
FROM table_1
LEFT JOIN table_2 ON table_1.col_pk = table_2.col_pk

要么

查詢2

UPDATE table_1
SET col_1 = value1
FROM table_1
LEFT JOIN table_2 ON table_1.col_pk = table_2.col_pk
WHERE table_1.col_pk IS NULL

UPDATE table_1
SET col_1 = value2
FROM table_1
INNER JOIN table_2 ON table_1.col_pk = table_2.col_pk

Answer 1

第一個查詢可能會具有更好的性能，因為它只需要對table_1和table_2進行一次掃描。