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SELECT  count(*)  FROM `rs-shr-al-analyticsz-prj-ebc1.anl_persona.cliente_persona` 
WHERE periodo="2023-04-01"
AND id_cliente_persona NOT IN 
  (
    SELECT id_cliente_persona FROM `rs-shr-al-analyticsz-prj-ebc1.anl_persona.cliente_persona` 
    WHERE periodo = "2023-03-01"
  )