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What is the difference between UNION and UNION ALL?
...cted columns need to be of the same data type.
Example: If we have two tables, 1) Employee and 2) Customer
Employee table data:
Customer table data:
UNION Example (It removes all duplicate records):
UNION ALL Example (It just concatenate records, not eliminate duplicates, so it...
How to select only date from a DATETIME field in MySQL?
I have a table in the MySQL database that is set up with DATETIME . I need to SELECT in this table only by DATE and excluding the time.
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When to use Hadoop, HBase, Hive and Pig?
.... It's a distributed, scalable, big data store, modelled after Google's BigTable. It stores data as key/value pairs.
Coming to Hive. It provides us data warehousing facilities on top of an existing Hadoop cluster. Along with that it provides an SQL like interface which makes your work easier, in ca...
What IDE to use for Python? [closed]
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On my smartphone browser, this table is completely unreadable.
– Axel
Nov 14 '14 at 7:53
82
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PostgreSQL: How to change PostgreSQL user password?
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The user is an object, not a string. Compare with ALTER TABLE "table_name" or even SELECT * FROM "table_name". You couldn't use single quotes in these contexts with tables, and it's the same with users/roles.
– P Daddy
Apr 13 '16 at 5:11
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How does Rails keep track of which migrations have run for a database?
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Rails creates a table in your database called schema_migrations to keep track of which migrations have run.
The table contains a single column, version. When Rails runs a migration, it takes the leading digits in the migration's file name a...
How do I bind Twitter Bootstrap tooltips to dynamically created elements?
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great! for use inside a table add container: 'body' to avoid extra width.
– shock_gone_wild
Jan 19 '16 at 16:31
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Where does PostgreSQL store the database?
...ory;
To see all the run-time parameters, use
show all;
You can create tablespaces to store database objects in other parts of the filesystem. To see tablespaces, which might not be in that data directory, use this query.
SELECT * FROM pg_tablespace;
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Repository Pattern Step by Step Explanation [closed]
...are persisted. All of the knowledge of persistence, including mapping from tables to objects, is safely contained in the repository.
Very often, you will find SQL queries scattered in the codebase and when you come to add a column to a table you have to search code files to try and find usages of a...
Run a single migration file
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Note that if you do this, it probably won't update the schema_migrations table, but it seems like that's what you want anyway.
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