官方文档里面做了如下说明: If multiple rows have identical values in the ORDER BY columns, the server is free to return those rows in any order, and may do so differently depending on the overall execution plan. In other
二、“order by”引发的乱序 经过一番排查,发现罪魁祸首其实是order by。当使用order by的字段存在多行相同值时,就会导致上面出现的乱序问题,这里我们来看下官方的解释[1]: ❝If multiple rows have identical values in theORDER BYcolumns, the server is free to return those rows in any order, ...
这种行为的一种表现是带有和不带有 LIMIT 的 ORDER BY 查询可能会以不同的顺序返回行,如本节后面所述。 原文: If multiple rows have identical values in the ORDER BY columns, the server is free to return those rows in any order, and may do so differently depending on the overall execution plan...
“If multiple rows have identical values in the ORDER BY columns, the server is free to return those rows in any order, and may do so differently depending on the overall execution plan. In other words, the sort order of those rows is nondeterministic with respect to the nonordered columns...
12 rows in set (0.00 sec) While this data is helpful, you want to perform a deeper assessment and sort the results for some specific columns. Since you worked on movies across a few different genres, you’re interested in knowing how well-received they were by movie-goers. Specifically,...
In this query, theORDER BYclause is used to sort the result set based on theagecolumn in descending order. Creating Composite Indexes To optimize the sorting process, we can create composite indexes on the relevant fields. Composite indexes are indexes that are created on multiple columns. They...
In this query, the index on(key_part1,key_part2)enables the optimizer to avoid sorting: SELECT*FROMt1ORDERBYkey_part1,key_part2; However, the query usesSELECT *, which may select more columns thankey_part1andkey_part2. In that case, scanning an entire index and looking up table rows...
(*) with order by multiple columns without where/group Simple SELECT with implicit grouping used to return many rows if the query was ordered by the aggregated column in the SELECT list. This was incorrect because queries with implicit grouping should only return a single record. The problem ...
The classCL_ABAP_DYN_PRGcontains methods that support the creation of correct and secure dynamically specified columns. The literals of the dynamically specified Open SQL statements can span multiple rows of a token specified dynamically as an internal table. ...
Model.objects.all().distinct('foo').order_by('bar') The above generates the following SQL: SELECTDISTINCTON("app_model"."foo")<lotsofcolumnshere>FROM"app_model"ORDERBY"app_model"."bar"ASC; I am not sure about all backends however the above syntax is not allowed in PostgreSQL which pr...