没有使用With子句或适当的连接并依赖子查询。

反模式:

select 
 ...
from data
where RECORD.STATE IN (
          SELECT STATEID
            FROM STATE
           WHERE NAME IN
                    ('Published to test',
                     'Approved for public',
                     'Published to public',
                     'Archived'
                    ))

好: 我喜欢使用with子句使我的意图更易于阅读。

with valid_states as (
          SELECT STATEID
            FROM STATE
           WHERE NAME IN
                    ('Published to test',
                     'Approved for public',
                     'Published to public',
                     'Archived'
                    )
select  ... from data, valid_states
where data.state = valid_states.state

最好的:

select 
  ... 
from data join states using (state)
where 
states.state in  ('Published to test',
                     'Approved for public',
                     'Published to public',
                     'Archived'
                    )

The Altered View - A view that is altered too often and without notice or reason. The change will either be noticed at the most inappropriate time or worse be wrong and never noticed. Maybe your application will break because someone thought of a better name for that column. As a rule views should extend the usefulness of base tables while maintaining a contract with consumers. Fix problems but don't add features or worse change behavior, for that create a new view. To mitigate do not share views with other projects and, use CTEs when platforms allow. If your shop has a DBA you probably can't change views but all your views will be outdated and or useless in that case. The !Paramed - Can a query have more than one purpose? Probably but the next person who reads it won't know until deep meditation. Even if you don't need them right now chances are you will, even if it's "just" to debug. Adding parameters lowers maintenance time and keep things DRY. If you have a where clause you should have parameters. The case for no CASE - SELECT CASE @problem WHEN 'Need to replace column A with this medium to large collection of strings hanging out in my code.' THEN 'Create a table for lookup and add to your from clause.' WHEN 'Scrubbing values in the result set based on some business rules.' THEN 'Fix the data in the database' WHEN 'Formating dates or numbers.' THEN 'Apply formating in the presentation layer.' WHEN 'Createing a cross tab' THEN 'Good, but in reporting you should probably be using cross tab, matrix or pivot templates' ELSE 'You probably found another case for no CASE but now I have to edit my code instead of enriching the data...' END

没有使用With子句或适当的连接并依赖子查询。

反模式:

select 
 ...
from data
where RECORD.STATE IN (
          SELECT STATEID
            FROM STATE
           WHERE NAME IN
                    ('Published to test',
                     'Approved for public',
                     'Published to public',
                     'Archived'
                    ))

好: 我喜欢使用with子句使我的意图更易于阅读。

with valid_states as (
          SELECT STATEID
            FROM STATE
           WHERE NAME IN
                    ('Published to test',
                     'Approved for public',
                     'Published to public',
                     'Archived'
                    )
select  ... from data, valid_states
where data.state = valid_states.state

最好的:

select 
  ... 
from data join states using (state)
where 
states.state in  ('Published to test',
                     'Approved for public',
                     'Published to public',
                     'Archived'
                    )

我最喜欢的SQL反模式:

对非唯一列进行JOIN，并使用SELECT DISTINCT修剪结果。

创建连接多个表的视图，只是为了从一个表中选择少数列。

 CREATE VIEW my_view AS 
     SELECT * FROM table1
     JOIN table2 ON (...)
     JOIN table3 ON (...);

 SELECT col1, col2 FROM my_view WHERE col3 = 123;

我最不喜欢的是

Using spaces when creating tables, sprocs etc. I'm fine with CamelCase or under_scores and singular or plurals and UPPERCASE or lowercase but having to refer to a table or column [with spaces], especially if [ it is oddly spaced] (yes, I've run into this) really irritates me. Denormalized data. A table doesn't have to be perfectly normalized, but when I run into a table of employees that has information about their current evaluation score or their primary anything, it tells me that I will probably need to make a separate table at some point and then try to keep them synced. I will normalize the data first and then if I see a place where denormalization helps, I'll consider it. Overuse of either views or cursors. Views have a purpose, but when each table is wrapped in a view it's too much. I've had to use cursors a few times, but generally you can use other mechanisms for this. Access. Can a program be an anti-pattern? We have SQL Server at my work, but a number of people use access due to it's availabilty, "ease of use" and "friendliness" to non-technical users. There is too much here to go into, but if you've been in a similar environment, you know.

使用@@IDENTITY代替SCOPE_IDENTITY()

引自以下回答:

@@IDENTITY returns the last identity value generated for any table in the current session, across all scopes. You need to be careful here, since it's across scopes. You could get a value from a trigger, instead of your current statement. SCOPE_IDENTITY returns the last identity value generated for any table in the current session and the current scope. Generally what you want to use. IDENT_CURRENT returns the last identity value generated for a specific table in any session and any scope. This lets you specify which table you want the value from, in case the two above aren't quite what you need (very rare). You could use this if you want to get the current IDENTITY value for a table that you have not inserted a record into.