大约有 6,000 项符合查询结果（耗时：0.0151秒） [XML]
Cast int to varchar
...m t9;
select CONVERT(id, CHAR(50)) as colI1
from t9;
See the following SQL — in action — over at SQL Fiddle:
/*! Build Schema */
create table t9 (id INT, name VARCHAR(55));
insert into t9 (id, name) values (2, 'bob');
/*! SQL Queries */
select CAST(id as CHAR(50)) as col1 from t9;
select C...
how to exclude null values in array_agg like in string_agg using postgres?
...
SQL Fiddle
select
id,
(select array_agg(a) from unnest(canonical_users) a where a is not null) canonical_users,
(select array_agg(a) from unnest(non_canonical_users) a where a is not null) non_canonical_users
fro...
How can I drop all the tables in a PostgreSQL database?
How can I drop all tables in PostgreSQL, working from the command line?
24 Answers
24
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刘强东“一元年薪”背后的O2O棋局 - 资讯 - 清泛网 - 专注C/C++及内核技术
...东将持有永辉超市10%的股份。并拥有提名永辉两名董事(包括一名
独立董事)的权利。双方将主要通过联合采购的方式，加强供应链管理能力，并会继续探索O2O等领域战略合作的发展机遇。
唐兴通认为，入股永辉超市是京东从物...
updating table rows in postgres using subquery
...FROM (SELECT address_id, customer, address, partn
FROM /* big hairy SQL */ ...) AS subquery
WHERE dummy.address_id=subquery.address_id;
This syntax is not standard SQL, but it is much more convenient for this type of query than standard SQL. I believe Oracle (at least) accepts something sim...
How do I execute inserts and updates in an Alembic upgrade script?
...rent connection, and make a session with it.
Or use bind.execute() to use SQLAlchemy's lower level to write SQL queries directly. This is useful for simple migrations.
Use the models and session as you normally would in your application.
"""create teams table
Revision ID: 169ad57156f0
Revises...
I need to generate uuid for my rails application. What are the options(gems) I have? [duplicate]
... UUID has RFC! This will break any UUID validation (like in PostgreSQL)
– kixorz
Feb 10 '14 at 8:05
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CASCADE DELETE just once
I have a Postgresql database on which I want to do a few cascading deletes. However, the tables aren't set up with the ON DELETE CASCADE rule. Is there any way I can perform a delete and tell Postgresql to cascade it just this once? Something equivalent to
...
Does PostgreSQL support “accent insensitive” collations?
In Microsoft SQL Server, it's possible to specify an "accent insensitive" collation (for a database, table or column), which means that it's possible for a query like
...
What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
...lly, a lot of dbms have been quite poor when it comes to handling joins (MySQL being a particularly noteworthy example). So n+1 has, often, been notably faster than a join. And then there are ways to improve on n+1 but still without needing a join, which is what the original problem relates to.
How...