进行测试后Postgres IS DISTINCT FROM，试听得到的最佳结果是什么，试听得到了相同的结果，COALESCE但用的时间更少：

SELECT COUNT(P.id)

FROM produto P
  INNER JOIN cliente CL ON P.id_cliente = CL.id_cliente

WHERE 
  COALESCE(CL.tp_pessoa,'') <> 'JURIDICA' -- test with COALESCE, average 610 ms

  (CL.tp_pessoa <> 'JURIDICA' OR CL.tp_pessoa IS NULL) -- test with OR, average 668 ms

  CL.tp_pessoa IS DISTINCT FROM 'JURIDICA' -- test with IS DISTINCT FROM, average 667 ms

  OUTRO TESTE:

  COALESCE(CL.tp_pessoa,'') <> COALESCE(P.observacao,'') -- test with IS DISTINCT FROM, average 940 ms

  CL.tp_pessoa IS DISTINCT FROM P.observacao -- test with ```IS DISTINCT FROM```, average 930 ms, a little beter here

它具有较低的性能，并且是其他DB中所没有的功能，例如SQL Server，不使用它的另一个原因。

做另一个可以同时满足两个条件的测试，NULL它IS DISTINCT FROM有一点优势，那就是它的使用，更多的应用呢？

编辑：

就像@hvd所说的那样，它是的一部分，ANSI SQL而的结果COALESCE(CL.tp_pessoa,'') <> COALESCE(P.observacao,'')并不相同CL.tp_pessoa IS DISTINCT FROM P.observacao。