Combine three SQL queries with keeping orders of the queries without duplicates-CodePudding

I have three queries as follows:

select * from orders where full_name like 'Mohammed Ali%' order by g_date desc

This will gives all names starting with Mohammed Ali (10 results)

select * from orders where full_name like '%Mohammed Ali%' order by g_date desc

All names have 'Mohammed Ali' in it (20 results)

select * from orders where full_name like '%Mohammed%Ali%' order by g_date desc

All names have Mohammed and Ali (100 results)

I would like to get results for all three queries, but the priority for the 1st query then the 2nd, and finally, the last. I don't want duplicate results.

I first did the following:

select * from (
select * from orders where full_name like 'Mohammed Ali%'order by g_date desc)
union
select * from (
select * from orders where full_name like '%Mohammed Ali%'order by g_date desc)
union
select * from (select * from orders where full_name like '%Mohammed%Ali%'order by g_date desc)

But, I got mixed results from the three queries :( . No duplicates - (100 results) Great!

Then, I tried the following:

select * from (
select *,0 as ord from orders where full_name like 'Mohammed Ali%')
union
select * from (
select *,1 as ord from orders where full_name like '%Mohammed Ali%')
union
select *,2 as ord from (select * from orders where full_name like '%Mohammed%Ali%')
order by ord,g_date desc

The first issue was fixed (Great). However, now I have duplicate results (10 20 100)

How can I get sorted results with no duplicates?

CodePudding user response：

The only condition that you need in the WHERE clause is full_name LIKE '%Mohammed%Ali%'.

In the ORDER BY clause you can sort the returned rows by boolean expressions/conditions:

SELECT * 
FROM orders 
WHERE full_name LIKE '%Mohammed%Ali%'
ORDER BY full_name LIKE 'Mohammed Ali%' DESC, -- first all names starting with 'Mohammed Ali'
         full_name LIKE '%Mohammed Ali%' DESC; -- then all names containing 'Mohammed Ali'
-- all the other names will be at the bottom of the resultset

CodePudding user response：

try a simpel case when

with orders (full_name)
as
(
select 'Mohammed Ali'
Union all select 'hMohammed Ali'
Union all select 'Mohammed Ali'
Union all select 'fMohammed Ali'
Union all select 'hMohammed fAlia'
)
select 
    *,
    case when full_name like 'Mohammed Ali%' then 1
    when full_name like '%Mohammed Ali%' then 2
    when full_name like '%Mohammed%Ali%' then 3
    end as ord
from 
    (
        select * from orders where full_name like '%Mohammed%Ali%'
    ) x
order by ord