大约有 40,000 项符合查询结果（耗时：0.0355秒） [XML]
PostgreSQL Autoincrement
...RT INTO foo (bar) values ('blah');
INSERT INTO foo (bar) values ('blah');
SELECT * FROM foo;
1,blah
2,blah
SERIAL is just a create table time macro around sequences. You can not alter SERIAL onto an existing column.
sha...
Possible to perform cross-database queries with PostgreSQL?
... executes a query in a remote database
dblink executes a query (usually a SELECT, but it can be any SQL
statement that returns rows) in a remote database.
When two text arguments are given, the first one is first looked up as
a persistent connection's name; if found, the command is executed on
that...
Location of my.cnf file on macOS
...m there, MySQLWorkbench can create them for you by:
Opening a connection
Selecting the 'Options File' under 'INSTANCE' in the menu.
MySQLWorkbench will search for my.cnf and if it can't find it, it'll create it for you
sh...
Check if table exists without using “select from”
Is there a way to check if a table exists without selecting and checking values from it?
17 Answers
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Is there any performance gain in indexing a boolean field?
...
It depends on the actual queries and the selectivity of the index/query combination.
Case A: condition WHERE isok = 1 and nothing else there:
SELECT *
FROM tableX
WHERE isok = 1
If the index is selective enough (say you have 1M rows and only 1k have isok = 1), ...
Inserting a Python datetime.datetime object into MySQL
...
when iserting into t-sql
this fails:
select CONVERT(datetime,'2019-09-13 09:04:35.823312',21)
this works:
select CONVERT(datetime,'2019-09-13 09:04:35.823',21)
easy way:
regexp = re.compile(r'\.(\d{6})')
def to_splunk_iso(dt):
"""Converts the datetime ...
How to store arrays in MySQL?
... retrieve a person and all of their fruit you can do something like this:
SELECT p.*, f.*
FROM person p
INNER JOIN person_fruit pf
ON pf.person_id = p.id
INNER JOIN fruits f
ON f.fruit_name = pf.fruit_name
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Maximum execution time in phpMyadmin
..._time = 5000
max_input_time = 5000
memory_limit = 1000M
And change xampp\mysql\bin\my.ini
max_allowed_packet = 200M
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Cast from VARCHAR to INT - MySQL
...NED [INTEGER]
TIME
UNSIGNED [INTEGER]
Therefore, you should use:
SELECT CAST(PROD_CODE AS UNSIGNED) FROM PRODUCT
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MySQL: Invalid use of group function
..., not WHERE.
The difference is: the WHERE clause filters which rows MySQL selects. Then MySQL groups the rows together and aggregates the numbers for your COUNT function.
HAVING is like WHERE, only it happens after the COUNT value has been computed, so it'll work as you expect. Rewrite your subque...