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Top Forums Shell Programming and Scripting What are $(...) and $((...)) used for? Post 302477382 by ctsgnb on Saturday 4th of December 2010 07:10:59 PM
Old 12-04-2010
$(...)evaluate the command that is inside and pass the result as a variable (new fashion) ... the old fashion way is using back tick ``
$((...))is used when evaluating arithmetic operation
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DROP 
TABLE(7) SQL Commands DROP TABLE(7) NAME
DROP TABLE - remove a table SYNOPSIS
DROP TABLE [ IF EXISTS ] name [, ...] [ CASCADE | RESTRICT ] DESCRIPTION
DROP TABLE removes tables from the database. Only its owner can drop a table. To empty a table of rows without destroying the table, use DELETE [delete(7)] or TRUNCATE [truncate(7)]. DROP TABLE always removes any indexes, rules, triggers, and constraints that exist for the target table. However, to drop a table that is referenced by a view or a foreign-key constraint of another table, CASCADE must be specified. (CASCADE will remove a dependent view entirely, but in the foreign-key case it will only remove the foreign-key constraint, not the other table entirely.) PARAMETERS
IF EXISTS Do not throw an error if the table does not exist. A notice is issued in this case. name The name (optionally schema-qualified) of the table to drop. CASCADE Automatically drop objects that depend on the table (such as views). RESTRICT Refuse to drop the table if any objects depend on it. This is the default. EXAMPLES
To destroy two tables, films and distributors: DROP TABLE films, distributors; COMPATIBILITY
This command conforms to the SQL standard, except that the standard only allows one table to be dropped per command, and apart from the IF EXISTS option, which is a PostgreSQL extension. SEE ALSO
ALTER TABLE [alter_table(7)], CREATE TABLE [create_table(7)] SQL - Language Statements 2010-05-14 DROP TABLE(7)
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