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Converting an array of objects to ActiveRecord::Relation
...rray to an ActiveRecord::Relation since a Relation is just a builder for a SQL query and its methods do not operate on actual data.
However, if what you want is a relation then:
for ActiveRecord 3.x, don’t call all and instead call scoped, which will give back a Relation which represents the sa...
NOT IN vs NOT EXISTS
...duce the row count to zero makes cardinality estimation very difficult. If SQL Server assumes that this will happen but in fact there were no NULL rows in the data the rest of the execution plan may be catastrophically worse, if this is just part of a larger query, with inappropriate nested loops ca...
How to truncate a foreign key constrained table?
...in PHPMYADMIN, this works only if you use all the transactions in the same SQL window (separated by a ;). This is because each fresh web SQL call will reset the FOREIGN_KEY_CHECKS to 1.
– Sablefoste
Oct 7 '13 at 21:17
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Oracle “(+)” Operator
I am checking some old SQL Statements for the purpose of documenting them and probably enhancing them.
4 Answers
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Relational Database Design Patterns? [closed]
...u want use in the future another DBMS? If yes then does not use to special SQL stuff of the current DBMS. Remove logic in your application.
Does not use:
white spaces in table names and column names
Non Ascii characters in table and column names
binding to a specific lower case or upper case. An...
Delete a single record from Entity Framework?
I have a SQL Server table in Entity Framework named employ with a single key column named ID .
15 Answers
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Are PostgreSQL column names case-sensitive?
...olumn names) that are not double-quoted are folded to lower case in PostgreSQL. Column names that were created with double-quotes and thereby retained upper-case letters (and/or other syntax violations) have to be double-quoted for the rest of their life: ("first_Name")
So, yes, PostgreSQL column n...
H2 in-memory database. Table not found
... Is it possible to set this DATABASE_TO_UPPER=false thing as an SQL statement in an init script? (Similarly as a statement like SET MODE PostgreSQL;) If so, what is the exact syntax?
– Jonik
Nov 4 '15 at 10:41
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DROP IF EXISTS VS DROP?
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Standard SQL syntax is
DROP TABLE table_name;
IF EXISTS is not standard; different platforms might support it with different syntax, or not support it at all. In PostgreSQL, the syntax is
DROP TABLE IF EXISTS table_name;
The fir...
How to get a list of column names on Sqlite3 database?
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Just to put this into code terms for SQLiteDatabase on Android, write db.rawQuery("PRAGMA table_info(" + tablename + ")", null);
– Noumenon
Jun 8 '13 at 14:14
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