Mysql – How to remove identical (but negative) rows that are also in some days of each other from a SELECT on a table

MySQLselect

I have a MySQL table with two fields: date and value. date is of type date, and value is decimal(10,2).

There are "pairs" of rows (non-consecutive) whose values are of equal magnitude but opposite sign, within 7 days of each other.

date        value
...
2020-06-20  123.45
...
2020-06-25  -123.45
...

The above is a "pair" because they are negatives of each other and their dates are within 7 days of each other. There may be any number of intervening rows. There may be any number of pairs in the table. Pairs of differing values may overlap 7 day periods. For simplicity assume there are no other equal-value rows also with 7 days (ie, no triples).

I'm trying to find a SELECT statement that gives me all the table's rows EXCEPT "pairs". Could someone please help?

Best Answer

SELECT *
FROM table t1
WHERE NOT EXISTS ( SELECT NULL
                   FROM TABLE t2
                   WHERE t2.`value` = -t1.`value`
                     AND t2.`date` BETWEEN t1.`date` - INTERVAL 7 DAY 
                                       AND t1.`date` + INTERVAL 7 DAY )

Related Solutions

MySQL 5.5 – Find Total Duration of Each Consecutive Series of Rows

Query 1, tested in SQLFiddle-1

SET @ward_id_to_check = 1 ;

SELECT
    st.patient_id,
    st.bed_id AS starting_bed_id,          -- the first bed a patient uses
                                           -- can be omitted
    st.admitted,
    MIN(en.discharged) AS discharged
FROM
  ( SELECT patient_id, bed_id, admitted, discharged
    FROM t 
    WHERE t.ward_id = @ward_id_to_check
      AND NOT EXISTS
          ( SELECT * 
            FROM t AS prev 
            WHERE prev.ward_id = @ward_id_to_check
              AND prev.patient_id = t.patient_id
              AND prev.discharged = t.admitted
          )
  ) AS st
JOIN
  ( SELECT patient_id, admitted, discharged
    FROM t 
    WHERE t.ward_id = @ward_id_to_check
      AND NOT EXISTS
          ( SELECT * 
            FROM t AS next 
            WHERE next.ward_id = @ward_id_to_check
              AND next.patient_id = t.patient_id
              AND next.admitted = t.discharged
          )
  ) AS en
    ON  st.patient_id = en.patient_id
    AND st.admitted <= en.admitted
GROUP BY
    st.patient_id,
    st.admitted ;

Query 2, which is the same as 1 but without the derived tables. This will probably have better execution plan, with proper indexes. Test in SQLFiddle-2:

SET @ward_id_to_check = 1 ;

SELECT
    st.patient_id,
    st.bed_id AS starting_bed_id,
    st.admitted,
    MIN(en.discharged) AS discharged
FROM
    t AS st    -- starting period
  JOIN
    t AS en    -- ending period
      ON  en.ward_id = @ward_id_to_check
      AND st.patient_id = en.patient_id
      AND NOT EXISTS
          ( SELECT * 
            FROM t AS next 
            WHERE next.ward_id = @ward_id_to_check
              AND next.patient_id = en.patient_id
              AND next.admitted = en.discharged
          )
      AND st.admitted <= en.admitted
WHERE 
      st.ward_id = @ward_id_to_check
  AND NOT EXISTS
      ( SELECT * 
        FROM t AS prev 
        WHERE prev.ward_id = @ward_id_to_check
          AND prev.patient_id = st.patient_id
          AND prev.discharged = st.admitted
      )
GROUP BY
    st.patient_id,
    st.admitted ;

Both queries assume that there is a unique constraint on (patient_id, admitted). If the server runs with strict ANSI settings, the bed_id should be added in the GROUP BY list.

Postgresql – Select rows from table where each row refers to a different schema

You could use inheritance for this. You would have a "master" schema with template tables and only the basic set of columns that all inheriting tables share:

CREATE TABLE master.portal(portal_name text);

All other tables in various schemata inherit from it, while possibly adding more local columns:

CREATE TABLE a.portal(portal_id serial PRIMARY KEY, col2 text)
INHERITS (master.portal);

CREATE TABLE b.portal(portal_id serial PRIMARY KEY, col2 text, col3 text)
INHERITS (master.portal);

A SELECT query targeted on the master table would then search all child tables as well:

SELECT portal_name, tableoid::regclass::text AS source
FROM   master.portal
WHERE  portal_name ILIKE '%test%';

More details in this closely related answer on SO:

Retrieve all records from multiple schemas in a PostgreSQL database

Best Answer

Related Solutions

MySQL 5.5 – Find Total Duration of Each Consecutive Series of Rows

Postgresql – Select rows from table where each row refers to a different schema

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