Question

I have a problem understandint ORDER BY in MySQL. I have to sort a table by 3 criteria

1 – first i want to sort by TYPE_OF_WORK so all data must be alphabetical, like

dech_rap_bus
dech_rap_bus
ger_dem_dech_bus
ger_dem_dech_bus
ger_dem_stp_pp
...

RESULT => http://sqlfiddle.com/#!2/b2a858/6

2 – second i want to sort by PROJECT_VERSION so all data must be alphabetical, but respecting the 1 criteria, like

dech_rap_bus            V123-V1234
dech_rap_bus            V300
ger_dem_dech_bus        V123-V1234  
ger_dem_dech_bus        V300
ger_dem_stp_pp          V123-V1234  

RESULT => http://sqlfiddle.com/#!2/b2a858/7

So 1 and 2 are working perfectly.

3 – and after this i want to sort by the column not_existing

RESULT => http://sqlfiddle.com/#!2/b2a858/5

and i don’t know what it really do, but i see no results … i just want that the

dech_rap_bus V300

where the NOT_EXISTING column is 1 to be at the end, and when are more of NOT_EXISTING = 1 to sort them all but at the end of the table.

I tought to myself that a UNION of 2 selects would help me

/* Selecting all data where  not_existing is not 1 or NULL ---> working good! */
(
    SELECT 
    * 
    FROM 
    atm_mti_view 
    WHERE 
    project_function='FRS01' AND 
    on_big_project_id = 12 AND
    (not_existing != 1 OR not_existing IS NULL)
    ORDER BY
    type_of_work ASC,
    project_version ASC
)

UNION

/* Selecting all data where  not_existing is 1 ---> working good! */
(
    SELECT 
    * 
    FROM 
    atm_mti_view 
    WHERE 
    project_function='FRS01' AND 
    on_big_project_id = 12 AND
    not_existing = 1
    ORDER BY
    type_of_work ASC,
    project_version ASC
)

but what this piece of code does, is putting the not existing dech_rap_bus at the end, good, but it messes up the version sorting, WHY???

SEE RESULT HERE => http://sqlfiddle.com/#!2/b2a858/8

Why is that? I just want to MERGE two select results, what i am doing wrong?

Answer 1

If you do

order by 
 (case when not_existing is null then 0 else not_existing end) desc
,type_of_work ASC,
project_version ASC

It will come first.

your query is not ordering because you have different project value for dech_rap_bus

TYPE_OF_WORK    PROJECT_VERSION 
dech_rap_bus    V123-V1234  
dech_rap_bus    V300