Mysql – SQL substract values from same column different rows

Just use GROUP_CONCAT with a WHERE condition

SELECT user_id,GROUP_CONCAT(meta_value ORDER BY id) 
FROM t 
WHERE meta_key  IN('first_name','last_name','street_add','city','state') 
GROUP BY user_id

To address this problem, I did the following (I'm using PostgreSQL for this, but SQL Server has CTEs and RECURSIVE CTEs and window/analytic functions. I doubt if this can be done in MySQL - maybe using variables - not sure). PostgreSQL is as powerful as the big boys - MySQL is really a toy!

Created a table:

CREATE TABLE stock (sku int, datein date, dateout date, status int);

Populated it thus:

INSERT INTO stock VALUES (123, '2015-02-01', '2015-02-05', 1);
INSERT INTO stock VALUES (123, '2015-02-10', '2015-02-10', 1);
INSERT INTO stock VALUES (123, '2015-02-20', NULL,         0);

Then, I constructed the first part of my query. The actual dates to and from will obviously vary depending on the requirements - I assumed that (from the sample data), the OP wanted to look at the month of February. I constructed the following RECURSIVE CTE to construct a list of the days in February - PostgreSQL has the nifty generate_series function, but that's proprietary and I wanted to make my query portable (to the greatest extent possible). This is the best explanation of RCTEs I came across.

WITH RECURSIVE dates (test_date) AS
(
  SELECT '2015-02-01'::DATE
  UNION ALL
  SELECT test_date + 1 FROM dates
  WHERE test_date < '2015-02-28'
)

Now, I thought that the organisation of the raw data was poor, so I used CTEs to rearrange the data.

Get the outdates from the raw data:

out_dates AS
(
  SELECT dateout AS dout FROM stock
)

Get the indates from the raw data:

in_dates AS
(
  SELECT datein AS din FROM stock
)

Then I "transpose" the data - have to use two steps because one cannot use a Window function in a WHERE clause

transpose AS
(
  SELECT lag(dateout) over() AS datein, datein AS dateout FROM stock
  -- WHERE lag(datein) over() IS NOT NULL AND dateout IS NOT NULL <<-- can't use here.
  ORDER BY dateout, datein
)

And then

ranges AS
(
  SELECT * FROM transpose
  WHERE datein IS NOT NULL AND dateout IS NOT NULL
),

The result of this query is:

datein|dateout
2015-02-05|2015-02-10
2015-02-18|2015-02-20

Note that this corresponds to the in and out dates, but now the data is much simpler to handle because it's structure is more logical - it's chronologically coherent - thanks to the use of the LAG window function.

Now, we bring it all together with the next query:

x AS
(
  SELECT test_date, CASE WHEN has_match THEN 1 ELSE 0 END::int AS flag
  FROM 
  (
    SELECT test_date, 
    EXISTS
    (
      SELECT 1 
      FROM ranges 
      WHERE dates.test_date BETWEEN ranges.datein AND ranges.dateout
    ) AS has_match
  FROM dates  
  ) range_checks
)
SELECT * FROM x;

This gives a series of records for the month that are of this form:

test_date|flag
--------------
2015-02-01|0
2015-02-02|0
2015-02-03|0
2015-02-04|0
2015-02-05|1
2015-02-06|1
<other records snipped for brevity>

or use this as the final query

z AS 
(
  SELECT * FROM dates d
  LEFT JOIN ranges r
  ON (d.test_date BETWEEN r.datein AND r.dateout)
)
SELECT * FROM z;

for records of this form:

test_date|datein|dateout
2015-02-01||
2015-02-02||
2015-02-03||
2015-02-04||
2015-02-05|2015-02-05|2015-02-10
2015-02-06|2015-02-05|2015-02-10
<rest of the records snipped for brevity>