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What is the purpose of Order By 1 in SQL select statement?
...number stands for the column based on the number of columns defined in the SELECT clause. In the query you provided, it means:
ORDER BY A.PAYMENT_DATE
It's not a recommended practice, because:
It's not obvious/explicit
If the column order changes, the query is still valid so you risk ordering ...
Best way to select random rows PostgreSQL
I want a random selection of rows in PostgreSQL, I tried this:
12 Answers
12
...
What is the most efficient/elegant way to parse a flat table into a tree?
...port recursive queries in standard syntax.
WITH RECURSIVE MyTree AS (
SELECT * FROM MyTable WHERE ParentId IS NULL
UNION ALL
SELECT m.* FROM MyTABLE AS m JOIN MyTree AS t ON m.ParentId = t.Id
)
SELECT * FROM MyTree;
I tested recursive queries in MySQL 8.0 in my presentation Recursive ...
Is there a combination of “LIKE” and “IN” in SQL?
...
An example table:
SQL> create table mytable (something)
2 as
3 select 'blabla' from dual union all
4 select 'notbla' from dual union all
5 select 'ofooof' from dual union all
6 select 'ofofof' from dual union all
7 select 'batzzz' from dual
8 /
Table created.
The origin...
What is the fastest/most efficient way to find the highest set bit (msb) in an integer in C?
...zeof(uint32_t));
return (tmp>>20)-1023;
Or in C99 and later, use a union {double d; uint32_t u[2];};. But note that in C++, union type punning is only supported on some compilers as an extension, not in ISO C++.
This will usually be slower than a platform-specific intrinsic for a leading...
How do I get the size of a java.sql.ResultSet?
...
Do a SELECT COUNT(*) FROM ... query instead.
OR
int size =0;
if (rs != null)
{
rs.last(); // moves cursor to the last row
size = rs.getRow(); // get row id
}
In either of the case, you won't have to loop over the enti...
Counting null and non-null values in a single query
...le and SQL Server (you might be able to get it to work on another RDBMS):
select sum(case when a is null then 1 else 0 end) count_nulls
, count(a) count_not_nulls
from us;
Or:
select count(*) - count(a), count(a) from us;
...
Is it possible to specify condition in Count()?
...an use the fact that the count aggregate only counts the non-null values:
select count(case Position when 'Manager' then 1 else null end)
from ...
You can also use the sum aggregate in a similar way:
select sum(case Position when 'Manager' then 1 else 0 end)
from ...
...
PreparedStatement IN clause alternatives?
... and cons of each is available here.
The suggested options are:
Prepare SELECT my_column FROM my_table WHERE search_column = ?, execute it for each value and UNION the results client-side. Requires only one prepared statement. Slow and painful.
Prepare SELECT my_column FROM my_table WHERE search_...
What's wrong with nullable columns in composite primary keys?
...ow in a table: when a table has a primary key, you have a guranteed way to select any row from it.
A unique constraint does not necessarily identify every row; it just specifies that if a row has values in its columns, then they must be unique. This is not sufficient to uniquely identify every row...