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Django in / not in query
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table1.objects.exclude(id__in=
table2.objects.filter(your_condition).values_list('id', flat=True))
The exclude function works like the Not operator you where asking for. The attribute flat = True tells to table2 query t...
SQL select join: is it possible to prefix all columns as 'prefix.*'?
I'm wondering if this is possible in SQL. Say you have two tables A and B, and you do a select on table A and join on table B:
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How to create relationships in MySQL
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If the tables are innodb you can create it like this:
CREATE TABLE accounts(
account_id INT NOT NULL AUTO_INCREMENT,
customer_id INT( 4 ) NOT NULL ,
account_type ENUM( 'savings', 'credit' ) NOT NULL,
balance FLOAT(...
Quickly reading very large tables as dataframes
I have very large tables (30 million rows) that I would like to load as a dataframes in R. read.table() has a lot of convenient features, but it seems like there is a lot of logic in the implementation that would slow things down. In my case, I am assuming I know the types of the columns ahead o...
Reorder / reset auto increment primary key
I have a MySQL table with an auto increment primary key. I deleted some rows in the middle of the table. Now I have, for example, something like this in the ID column: 12, 13, 14, 19, 20. I deleted the 15, 16, 17 and 18 rows.
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How to get number of entries in a Lua table?
.... The Lua # operator only counts entries with integer keys, and so does table.getn :
8 Answers
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Is it possible to for SQL Output clause to return a column not being inserted?
...modifications to my database and I need to migrate the old data to the new tables. For that, I need to fill a table (ReportOptions) taking the data from the original table (Practice), and fill a second intermediate table (PracticeReportOption).
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What is the difference between JOIN and UNION?
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Joins and Unions can be used to combine data from one or more tables. The difference lies in how the data is combined.
In simple terms, joins combine data into new columns. If two tables are joined together, then the data from the first table is shown in one set of column alongside t...
How to select only 1 row from oracle sql?
I want to use oracle syntax to select only 1 row from table DUAL . For example, I want to execute this query:
13 Answers
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Disable all table constraints in Oracle
How can I disable all table constrains in Oracle with a single command?
This can be either for a single table, a list of tables, or for all tables.
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