大约有 40,000 项符合查询结果（耗时：0.0395秒） [XML]
How do I get a list of column names from a psycopg2 cursor?
... If you just want the column names, don't select all of the rows in the table. This is more efficient: curs.execute("SELECT * FROM people LIMIT 0")
– Demitri
Sep 6 '12 at 22:03
...
Create a table without a header in Markdown
Is it possible to create a table without a header in Markdown?
11 Answers
11
...
Bulk insert with SQLAlchemy ORM
...scoped_session(sessionmaker())
engine = None
class Customer(Base):
__tablename__ = "customer"
id = Column(Integer, primary_key=True)
name = Column(String(255))
def init_sqlalchemy(dbname='sqlite:///sqlalchemy.db'):
global engine
engine = create_engine(dbname, echo=False)
...
Only read selected columns
...hs (7 columns) for each year of the data below, for example by using read.table() ?
4 Answers
...
SQLAlchemy: print the actual query
...'literal_binds' flag, passed to compile_kwargs:
from sqlalchemy.sql import table, column, select
t = table('t', column('x'))
s = select([t]).where(t.c.x == 5)
print(s.compile(compile_kwargs={"literal_binds": True}))
the above approach has the caveats that it is only supported for basic
types, su...
Best practices for in-app database migration for Sqlite
...anges aren't committed.
For making schema changes, sqlite supports "ALTER TABLE" syntax for certain operations (renaming the table or adding a column). This is an easy way to update existing tables in-place. See the documentation here: http://www.sqlite.org/lang_altertable.html. For deleting col...
Rails :include vs. :joins
...
.joins will just joins the tables and brings selected fields in return. if you call associations on joins query result, it will fire database queries again
:includes will eager load the included associations and add them in memory. :includes loads all...
How to change collation of database, table, column?
...
You need to either convert each table individually:
ALTER TABLE mytable CONVERT TO CHARACTER SET utf8mb4
(this will convert the columns just as well), or export the database with latin1 and import it back with utf8mb4.
...
Efficiently convert rows to columns in sql server
...Code, LastName, AccountNumber
from
(
select value, columnname
from yourtable
) d
pivot
(
max(value)
for columnname in (Firstname, Amount, PostalCode, LastName, AccountNumber)
) piv;
See Demo.
Pivot with unknown number of columnnames
If you have an unknown number of columnnames that you w...
Case insensitive searching in Oracle
...ur data to be the same case by using UPPER() or LOWER():
select * from my_table where upper(column_1) = upper('my_string');
or
select * from my_table where lower(column_1) = lower('my_string');
If column_1 is not indexed on upper(column_1) or lower(column_1), as appropriate, this may force a f...