大约有 6,100 项符合查询结果（耗时：0.0205秒） [XML]
Select where count of one field is greater than one
...e result comparison.
Taking the query at face value:
SELECT *
FROM db.table
HAVING COUNT(someField) > 1
Ideally, there should be a GROUP BY defined for proper valuation in the HAVING clause, but MySQL does allow hidden columns from the GROUP BY...
Is this in preparation for a unique cons...
MySQL maximum memory usage
...the (f'ing) manual.
As for the database -- a few important constraints:
table engine (InnoDB, MyISAM, ...)
size
indices
usage
Most MySQL tips on stackoverflow will tell you about 5-8 so called important settings. First off, not all of them matter - e.g. allocating a lot of resources to InnoDB a...
How to find a text inside SQL Server procedures / triggers?
...
Just be aware that the syscomments table stores the values in 8000-character chunks, so if you are unlucky enough to have the text you're searching for split across one of these boundaries, you won't find it with this method.
– ErikE
...
Mean per group in a data.frame [duplicate]
...ype of operation is exactly what aggregate was designed for:
d <- read.table(text=
'Name Month Rate1 Rate2
Aira 1 12 23
Aira 2 18 73
Aira 3 19 45
Ben 1 53 19
Ben 2 22 87
Ben 3 19 ...
MySQL - UPDATE query based on SELECT Query
I need to check (from the same table) if there is an association between two events based on date-time.
11 Answers
...
Importing a CSV file into a sqlite3 database table using Python
...nge to 'sqlite:///your_filename.db'
cur = con.cursor()
cur.execute("CREATE TABLE t (col1, col2);") # use your column names here
with open('data.csv','r') as fin: # `with` statement available in 2.5+
# csv.DictReader uses first line in file for column headings by default
dr = csv.DictReader(...
Oracle PL/SQL - How to create a simple array variable?
...n Oracle PL/SQL that uses pure memory, they all seem to be associated with tables. I'm looking to do something like this in my PL/SQL (C# syntax):
...
Foreign key constraints: When to use ON UPDATE and ON DELETE
...eign key constraints are quite advanced.
We'll take an example, a company table with a user table containing people from theses company
CREATE TABLE COMPANY (
company_id INT NOT NULL,
company_name VARCHAR(50),
PRIMARY KEY (company_id)
) ENGINE=INNODB;
CREATE TABLE USER (
user_...
Python SQL query string formatting
...Code Sample:
sql = ("SELECT field1, field2, field3, field4 "
"FROM table "
"WHERE condition1=1 "
"AND condition2=2;")
Works as well with f-strings:
fields = "field1, field2, field3, field4"
table = "table"
conditions = "condition1=1 AND condition2=2"
sql = (f"SELECT {fields...
What is the most efficient way to store tags in a database?
... items. This implies to me that you'll quite possibly need an intermediary table to overcome the many-to-many obstacle.
Something like:
Table: Items
Columns: Item_ID, Item_Title, Content
Table: Tags
Columns: Tag_ID, Tag_Title
Table: Items_Tags
Columns: Item_ID, Tag_ID
It might be that your web...