从表中选择第二个表中没有相关条目的行

Question

That's my first day in SQL using PostgreSQL 9.4 and I'm lost with some things. I think that I'm close but not enough:

Table definition:

CREATE TABLE DOCTOR (
    Doc_Number INTEGER,
    Name    VARCHAR(50) NOT NULL,
    Specialty   VARCHAR(50) NOT NULL,
    Address VARCHAR(50) NOT NULL,
    City    VARCHAR(30) NOT NULL,
    Phone   VARCHAR(10) NOT NULL,
    Salary  DECIMAL(8,2) NOT NULL,
    DNI     VARCHAR(10) UNIQUE
    CONSTRAINT pk_Doctor PRIMARY KEY (Doc_Number)
  );

CREATE TABLE VISIT (
    Doc_Number    INTEGER,
    Pat_Number    INTEGER,
    Visit_Date    DATE,
    Price           DECIMAL(7,2),
    CONSTRAINT Visit_pk PRIMARY KEY (Doc_Number, Pat_Number, Visit_Date),
    CONSTRAINT Visit_Doctor_fk FOREIGN KEY (Doc_Number) REFERENCES DOCTOR(Doc_Number),
    CONSTRAINT Visit_PATIENT_fk FOREIGN KEY (Pat_Number) REFERENCES PATIENT(Pat_Number)
  );

I need how to join these two queries into one:

SELECT d.City, d.Name
FROM DOCTOR d, VISIT v
WHERE d.Specialty = 'family and comunity' 
ORDER BY d.Name;

SELECT * FROM VISIT
WHERE DATE (Visit_Date)<'01/01/2012' 
            OR DATE(Visit_Date)>'31/12/2013';

I tried something like this but it doesn't work. I need the doctors of that specialty that didn't do any visit in 2012 and 2013.

SELECT City, Name
FROM DOCTOR d
WHERE d.Specialty = 'family and comunity' 
      AND NOT IN(SELECT *
        FROM VISIT 
        WHERE Visit_Date BETWEEN '2012-01-01' and '2013-12-31')
ORDER BY d.Name;

Can anyone help?

Answer 1

SELECT d.name, d.city
FROM   doctor     d
LEFT   JOIN visit v ON v.doc_number = d.doc_number
                   AND v.visit_date BETWEEN '2012-01-01' AND '2013-12-31'
WHERE  d.specialty = 'family and community'  -- or 'family and comunity'?
AND    v.doc_number IS NULL
ORDER  BY d.name;

• As commented you need a join condition. How are visits connected to doctors? Typically, you would have a visit.doctor_id referencing doctor.doctor_id .

• Using LEFT JOIN / IS NULL to rule out doctors who have visits in said period. This is one of several possible techniques:

  • Select rows which are not present in other table

• Dates must be greater than the lower bound AND smaller than the upper bound. OR would be wrong here.

• It's better to use ISO 8601 date format which is unambiguous regardless of your locale.

  • field value between date range

Answer 2

Alternative to the LEFT JOIN ... WHERE NULL construct is the plain WHERE NOT EXISTS(...) anti-join. [It is completely equivalent to erwin's query]

SELECT d.name, d.city
FROM   doctor  d
WHERE  d.specialty = 'family and community'
AND NOT EXISTS (
    SELECT 13
    FROM visit v WHERE v.doc_number = d.doc_number
                   AND v.visit_date BETWEEN '2012-01-01' AND '2013-12-31'
    )
ORDER  BY d.name;

Answer 3

You were almost there... Instead of

SELECT City, Name
FROM DOCTOR d
WHERE d.Specialty = 'family and comunity' 
      AND NOT IN(SELECT *
        FROM VISIT 
        WHERE Visit_Date BETWEEN '2012-01-01' and '2013-12-31')
ORDER BY d.Name;

try

SELECT City, Name
FROM DOCTOR d
WHERE d.Specialty = 'family and comunity' 
      AND doc_number NOT IN(SELECT doc_number -- or SELECT DISTINCT doc number - to get fewer rows from the subquery
        FROM VISIT 
        WHERE Visit_Date BETWEEN '2012-01-01' and '2013-12-31')
ORDER BY d.Name;

Just in case - table/column names are case-insensitive by default in Postgres. If you want them case sensitive - you have to write them in "" .

Answer 4

I finally found the solution, this is quite similar to your solutions, I post here to help another people with similar problems

SELECT City, Name
FROM DOCTOR d, VISIT v
WHERE d.Specialty = 'family and comunity' 
          AND not exists(SELECT *
          FROM visit v WHERE v.doc_number = d.doc_number
          AND v.visit_date BETWEEN '2012-01-01' AND '2013-12-31')      
GROUP BY name, city
ORDER BY d.Name;

Thank you all for your help!