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Pandas dataframe get first row of each group
...
>>> df.groupby('id').first()
value
id
1 first
2 first
3 first
4 second
5 first
6 first
7 fourth
If you need id as column:
>>> df.groupby('id').first().reset_index()
id value
0 1 first
1 ...
On delete cascade with doctrine2
...e to the foreign key column in the database:
@ORM\JoinColumn(name="father_id", referencedColumnName="id", onDelete="CASCADE")
I also want to point out that the way you have your cascade={"remove"} right now, if you delete a Child object, this cascade will remove the Parent object. Clearly not wha...
SQL Server query to find all permissions/access for all users in a database
...at a query, based on Andomar's suggestions. This query is intended to provide a list of permissions that a user has either applied directly to the user account, or through
roles that the user has.
/*
Security Audit Report
1) List all access provisioned to a sql user or windows user/group directly ...
How to convert JSON string to array
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If you pass the JSON in your post to json_decode, it will fail. Valid JSON strings have quoted keys:
json_decode('{foo:"bar"}'); // this fails
json_decode('{"foo":"bar"}', true); // returns array("foo" => "bar")
json_decode('{"foo":"bar"}'); // returns an object, not an arr...
When to use Common Table Expression (CTE)
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Interesting fact about CTE. I always wondered why NEWID() in the CTE changes when the CTE is referenced more than once. select top 100 * into #tmp from master..spt_values order by 1,2,3,4 select A.number, COUNT(*) from #tmp A inner join #tmp B ON A.number = B.number+1 group by...
SQL Server add auto increment primary key to existing table
...ting table which is already populated with 150000 records. I have added an Id column (which is currently null).
15 Answers
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How do I get a list of all the duplicate items using pandas in python?
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Method #1: print all rows where the ID is one of the IDs in duplicated:
>>> import pandas as pd
>>> df = pd.read_csv("dup.csv")
>>> ids = df["ID"]
>>> df[ids.isin(ids[ids.duplicated()])].sort("ID")
ID ENROLLMENT_DATE ...
Rails: Using greater than/less than with a where statement
I'm trying to find all Users with an id greater than 200, but I'm having some trouble with the specific syntax.
9 Answers
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Delete sql rows where IDs do not have a match from another table
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Using LEFT JOIN/IS NULL:
DELETE b FROM BLOB b
LEFT JOIN FILES f ON f.id = b.fileid
WHERE f.id IS NULL
Using NOT EXISTS:
DELETE FROM BLOB
WHERE NOT EXISTS(SELECT NULL
FROM FILES f
WHERE f.id = fileid)
Using NOT IN:
DELETE FROM BLOB
WHERE fi...
How to annotate MYSQL autoincrement field with JPA annotations
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To use a MySQL AUTO_INCREMENT column, you are supposed to use an IDENTITY strategy:
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
private Long id;
Which is what you'd get when using AUTO with MySQL:
@Id @GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
Which is a...