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Kingbasees SQL language reference manual of Jincang database (17. SQL statement: discard to drop language)

2022-07-26 19:59:00 【Thousands of sails passed by the side of the sunken boat_】

17. SQL sentence : DISCARD To DROP LANGUAGE

This chapter contains the following SQL sentence :

17.1. DISCARD

purpose

DISCARD — Discard session state

DISCARD Release internal resources related to a database session . This command helps to partially or completely reset the state of the session . There are several subcommands to release different types of resources .DISCARD ALL Variants include all other forms , It will also reset additional states .

precondition

nothing

grammar 

DISCARD { ALL | PLANS | SEQUENCES | TEMPORARY | TEMP }

semantics

PLANS

Release all cached query plans , Force you to reschedule the next time you use the relevant preparation statement .

SEQUENCES

Discard all cached sequence related states , Include ``currval()``/lastval() Information and anything that has not been nextval() The pre allocated sequence value returned （ See  CREATE SEQUENCE ）;

TEMPORARY or TEMP

Delete all temporary tables created in the current session .

ALL

Release all temporary resources related to the current session and reset the session to its initial state . Currently, this has the same effect as executing the following statement sequence ：

CLOSE ALL;
SET SESSION AUTHORIZATION DEFAULT;
RESET ALL;
DEALLOCATE ALL;
UNLISTEN *;
SELECT sys_advisory_unlock_all();
DISCARD PLANS;
DISCARD TEMP;
DISCARD SEQUENCES;

Example 

DISCARD SEQUENCES;

Compatibility

DISCARD It's a kind of KingbaseES Expand .

other

DISCARD ALL Cannot execute within a transaction block .

17.2. DO

purpose

DO — Execute an anonymous code block

DO Execute an anonymous code block , Or in other words, execute an instantaneous anonymous function written in a process language .

The code block is like a code block that has no parameters and returns void The function body of the function of . It will be parsed and executed in one time .

Optional LANGUAGE Clause can be unloaded before or after the code block .

precondition

The process language to be used must already be used CREATE LANGUAGE Installed in the current database . It is installed by default plsql, But other languages are not installed .

The user must have the USAGE Privilege , If the language is untrusted, it must be a super user . This is the same as the privilege requirements for creating a function in this language .

grammar 

DO [ LANGUAGE lang_name ] code

semantics

code

The process language code to be executed . As in the ``CREATE FUNCTION`` In the same , It must be specified as a string . It is recommended to use a dollar quoted text .

lang_name

The name of the process language that wrote the code . If omitted , The default is plsql.

Example

Put the pattern public All privileges on all views in are granted to roles webuser：

DO $$DECLARE r record;
BEGIN
        FOR r IN SELECT table_schema, table_name FROM information_schema.tables
                        WHERE table_type = 'VIEW' AND table_schema = 'public'
        LOOP
                EXECUTE 'GRANT ALL ON ' || quote_ident(r.table_schema) || '.' ||
                quote_ident(r.table_name) || ' TO webuser';
        END LOOP;
END$$;

Compatibility

SQL There is no in the standard DO sentence .

17.3. DROP ACCESS METHOD

purpose

DROP ACCESS METHOD — Remove an access method

DROP ACCESS METHOD Remove an existing access method .

precondition

Only super users can delete access methods .

grammar 

DROP ACCESS METHOD [ IF EXISTS ] name [ CASCADE | RESTRICT ]

semantics

IF EXISTS

If the access method does not exist , No error will be thrown . In this case, a prompt will be issued .

name

The name of an existing access method .

CASCADE

Automatically delete objects that depend on this access method （ For example, operator class 、 Operator family and index ）, And then delete all objects that depend on those objects （ see   Rely on tracking  ）.

RESTRICT

If any object depends on this access method , Then refuse to delete it . This is the default setting .

Example

Delete access method heptree：

DROP ACCESS METHOD heptree;

Compatibility

DROP ACCESS METHOD It's a kind of KingbaseES Expand .

17.4. DROP AGGREGATE

purpose

DROP AGGREGATE — Remove an aggregate function

DROP AGGREGATE Remove an existing aggregate function .

precondition

To execute this command , The current user must be the owner of the aggregation function .

grammar 

DROP AGGREGATE [ IF EXISTS ] name ( aggregate_signature ) [, ...] [ CASCADE | RESTRICT ]

 here aggregate_signature yes ：

* |
[ argmode ] [ argname ] argtype [ , ... ] |
[ [ argmode ] [ argname ] argtype [ , ... ] ] ORDER BY [ argmode ] [ argname ] argtype [ , ... ]

semantics

IF EXISTS

If the aggregation does not exist, do not throw an error , It's a reminder .

name

The name of an existing aggregate function （ It can be pattern Limited ）.

argmode

A parameter mode ：IN or VARIADIC. If it's ignored , The default value is IN.

argname

The name of a parameter . Be careful ``DROP AGGREGATE`` Don't really care about parameter names , Because only the parameter data type is needed to determine the identity of the aggregation function .

argtype

An input data type that the aggregate function operates on . To reference an aggregate function with zero parameters , Write ``*`` To replace the parameter description list . To reference an ordered set aggregation function , Write ORDER BY.

CASCADE

Automatically delete objects that depend on the aggregate function （ For example, use its view ）, Then delete all objects that depend on those objects （ see   Rely on tracking  ）.

RESTRICT

If any object depends on the aggregate function , Then refuse to delete it . This is the default .

Example

Type integer Remove the aggregate function myavg：

DROP AGGREGATE myavg(integer);

To remove the hypothetical set aggregation function myrank, This function receives an arbitrary list of permutations and a matching list of direct parameters ：

DROP AGGREGATE myrank(VARIADIC "any" ORDER BY VARIADIC "any");

To delete multiple aggregate functions in one command ：

DROP AGGREGATE myavg(integer), myavg(bigint);

Compatibility

stay SQL There is no in the standard DROP AGGREGATE sentence .

other

ALTER AGGREGATE  The following describes another syntax for referencing ordered set aggregation .

17.5. DROP CAST

purpose

DROP CAST — Remove a shape

DROP CAST Remove a previously defined shape .

precondition

To be able to delete a shape , You must have source data type or target data type . This is also the privilege required to create a shape .

grammar 

DROP CAST [ IF EXISTS ] (source_type AS target_type) [ CASCADE | RESTRICT ]

semantics

IF EXISTS

If the shape doesn't exist, don't throw an error , It's a reminder .

source_type

The name of the source data type of the shape .

target_type

Name of the target data type of the shape .

CASCADE

This keyword has no effect , Because there is no dependence on the shape .

RESTRICT

This keyword has no effect , Because there is no dependence on the shape .

Example

To remove from type text To type int The modelling of ：

DROP CAST (text AS int);

Compatibility

DROP CAST The command conforms to SQL standard .

17.6. DROP COLLATION

purpose

DROP COLLATION — Remove a collation

DROP COLLATION Remove a previously defined collation .

precondition

To be able to delete a collation , You must have it .

grammar 

DROP COLLATION [ IF EXISTS ] name [ CASCADE | RESTRICT ]

semantics

IF EXISTS

If the collation does not exist, do not throw an error , It's a reminder .

name

The name of the collation . The collation name can be schema qualified .

CASCADE

Automatically delete objects that depend on the collation , Then delete all objects that depend on those objects （ see   Rely on tracking  ）.

RESTRICT

If any object depends on the collation , Then refuse to delete it . This is the default .

Example

To delete the name german Collation of ：

DROP COLLATION german;

Compatibility

except IF EXISTS Beyond the options , DROP COLLATION The command conforms to SQL standard . This option is a KingbaseES Expand .

17.7. DROP CONTEXT

purpose

DROP CONTEXT Delete context（userenv Cannot delete ）. This information will be from pg_context In the table to delete .

Delete context Will not make this context Set up under key-value invalid . however , When the user next attempts to set this context when , The context Will be invalid . That is, it deletes the dictionary object , The instance object will not be deleted .

precondition

Have the permission to delete objects .

grammar 

DROP CONTEXT namespace

semantics

namespace

Specify the... To delete context name . Cannot delete built-in context userenv.

Example

To delete the name context_test Of context：

drop context context_test;

17.8. DROP CONVERSION

purpose

DROP CONVERSION — Remove a transformation

DROP CONVERSION Remove a previously defined transformation .

precondition

To be able to delete a transformation , You must have this conversion .

grammar 

DROP CONVERSION [ IF EXISTS ] name [ CASCADE | RESTRICT ]

semantics

IF EXISTS

If the transformation does not exist, do not throw an error , It's a reminder .

name

The name of the transformation . The transformation name can be schema qualified .

CASCADE

This keyword has no effect , Because there is no dependency on transformation .

RESTRICT

This keyword has no effect , Because there is no dependency on transformation .

Example

To delete the name myname Transformation ：

DROP CONVERSION myname;

Compatibility

stay SQL There is no in the standard DROP CONVERSION sentence , But there is one DROP TRANSLATION sentence . And the corresponding CREATE TRANSLATION sentence , It is associated with KingbaseES Medium CREATE CONVERSION  Sentence similarity .

17.9. DROP DATABASE

purpose

DROP DATABASE Remove a database . It will Remove the system directory entry of the database and delete the file directory containing the data . It can only be controlled by the database The owner executes . also , When you or anyone else has connected to the target database , It can't Be performed （ Connect to kingbase Or any other database to send this An order ）.

DROP DATABASE Cannot be revoked . Please use with care ！

precondition

You must have this database to use DROP DATABASE .

grammar 

DROP DATABASE [ IF EXISTS ] name

semantics

IF EXISTS

If the database does not exist, do not throw an error , It's a reminder .

name

Name of the database to be removed .

Example

Delete database mydatabase

DROP DATABASE mydatabase;

Compatibility

SQL There is no in the standard DROP DATABASE sentence .

other

DROP DATABASE Cannot execute within a transaction block .

When connecting to the target database , This command cannot be executed . therefore , Use the program  dropdb  Will be more convenient , It is a wrapper for this command .

17.10. DROP DATABASE LINK

purpose

DROP DATABASE LINK Remove a database link. database link Can be owned and DBA Delete , Delete database link After object , All objects in the user session will be cleared .

If database link Being used by other users , Cannot delete this database link.

Temporary does not support PUBLIC keyword .

precondition

To execute this command, you must have this database link Authority .

grammar 

DROP DATABASE LINK dblink_name

semantics

dblink_name

To delete DATABASE LINK name , You can include the schema name .

Example

Delete mydblink

DROP DATABASE LINK mydblink;

17.11. DROP DIRECTORY

purpose

DROP DIRECTORY Remove a directory .

precondition

Only superuser You can remove directories .

grammar 

DROP DIRECTORY [ IF EXISTS ] (public.)dir_name

semantics

IF EXISTS

If the directory does not exist, do not throw an error , It's a reminder .

dir_name

The name of an existing directory （ The default is public Pattern , Can be specified as public Pattern , Specify other modes to report errors ）.

Example

To remove a directory ：

DROP DIRECTORY dir_name;

Compatibility

except IF EXISTS Options , This command conforms to SQL standard . This option is a KingbaseES Expand .

17.12. DROP DOMAIN

purpose

DROP DOMAIN — Remove a domain

DROP DOMAIN Remove a domain .

precondition

Only the owner of the domain To remove it .

grammar 

DROP DOMAIN [ IF EXISTS ] name [, ...] [ CASCADE | RESTRICT ]

semantics

IF EXISTS

If the domain does not exist, do not throw an error , It's a reminder .

name

The name of an existing domain （ It can be pattern Limited ）.

CASCADE

Automatically delete objects that depend on this domain （ For example, table columns ）, Then delete all objects that depend on those objects （ see   Rely on tracking  ）.

RESTRICT

If any object depends on this domain , Then refuse to delete it . This is the default .

Example

To remove a domain box：

DROP DOMAIN box;

Compatibility

except IF EXISTS Options , This command conforms to SQL standard . This option is a KingbaseES Expand .

17.13. DROP EVENT TRIGGER

purpose

DROP EVENT TRIGGER — Remove an event trigger

precondition

To execute this command , The current user must be the owner of the event trigger .

grammar 

DROP EVENT TRIGGER [ IF EXISTS ] name [ CASCADE | RESTRICT ]

semantics

IF EXISTS

If the event trigger does not exist, do not throw an error , It's a reminder .

name

Name of the event trigger to remove .

CASCADE

Automatically delete objects that depend on this trigger , Then delete all objects that depend on those objects （ see   Rely on tracking  ）.

RESTRICT

If any object depends on this trigger , Then refuse to delete it . This is the default .

Example

Destroy trigger snitch：

DROP EVENT TRIGGER snitch;

Compatibility

stay SQL There is no in the standard DROP EVENT TRIGGER sentence .

17.14. DROP EXTENSION

purpose

DROP EXTENSION — Remove an extension

DROP EXTENSION Remove the extension from the database . Deleting an extension will cause its constituent objects to be deleted .

precondition

You must have this extension to use DROP EXTENSION.

grammar 

END [ WORK | TRANSACTION ] [ AND [ NO ] CHAIN ]

semantics

IF EXISTS

If the extension does not exist, do not throw an error , It's a reminder .

name

Name of an installed extension .

CASCADE

Automatically delete objects that depend on this extension , Then delete all objects that depend on those objects （ see   Rely on tracking  ）.

RESTRICT

If any object depends on this extension （ Instead of having its own member objects and others listed in the same DROP Extensions in the command ）, Then refuse to delete it . This is the default .

Example

To remove an extension from the current database hstore：

DROP EXTENSION hstore;

If hstore Any object of is in use in this database , For example, the column of a table is hstore type , This command will fail . add CASCADE Option can force these dependent objects to be removed .

Compatibility

DROP EXTENSION It's a KingbaseES Expand .

17.15. DROP FOREIGN DATA WRAPPER

purpose

DROP FOREIGN DATA WRAPPER — Remove an external data wrapper

DROP FOREIGN DATA WRAPPER Remove an existing external data wrapper .

precondition

To execute this command , The current user must be the owner of the external data wrapper .

grammar 

DROP FOREIGN DATA WRAPPER [ IF EXISTS ] name [, ...] [ CASCADE | RESTRICT ]

semantics

IF EXISTS

If the external data wrapper does not exist, do not throw an error , It's a reminder .

name

The name of an existing external data wrapper .

CASCADE

Automatically delete objects that depend on the external data wrapper （ For example, server ）, Then delete all objects that depend on those objects （ see   Rely on tracking  ）.

RESTRICT

If any object depends on the external data wrapper , Then refuse to delete it . This is the default .

Example

Delete external data wrapper dbi：

DROP FOREIGN DATA WRAPPER dbi;

Compatibility

DROP FOREIGN DATA WRAPPER  accord with ISO/IEC 9075-9 (SQL/MED).IF EXISTS Clause It's a KingbaseES Expand .

17.16. DROP FOREIGN TABLE

purpose

DROP FOREIGN TABLE — Remove an external table

DROP FOREIGN TABLE Remove an external table .

precondition

Only the owner of an external table can remove it .

grammar 

DROP FOREIGN TABLE [ IF EXISTS ] name [, ...] [ CASCADE | RESTRICT ]

semantics

IF EXISTS

If the external table does not exist, do not throw an error , It's a reminder .

name

Name of the external table to delete （ It can be pattern Limited ）.

CASCADE

Automatically delete objects that depend on the external table （ For example, view ）, Then delete all objects that depend on those objects （ see   Rely on tracking  ）.

RESTRICT

If any object depends on the external table , Then refuse to delete it . This is the default .

Example

To destroy two external tables films  and distributors：

DROP FOREIGN TABLE films, distributors;

Compatibility

This command conforms to ISO/IEC 9075-9 (SQL/MED), However, the standard allows only one external table to be deleted in each command without IF EXISTS Options . This option is a KingbaseES Expand .

17.17. DROP FUNCTION

purpose

DROP FUNCTION Remove the definition of an existing function . The parameter type of this function must be specified , Because many different functions may have the same function name and different parameter lists .

precondition

To execute this command, the user must be the owner of the function .

grammar 

DROP FUNCTION [ IF EXISTS ] name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ] [, ...] [ CASCADE | RESTRICT ]

semantics

IF EXISTS

If the function does not exist, do not throw an error , It's a reminder .

name

The name of an existing function （ It can be pattern Limited ）. If no parameter list is specified , Then the name must be unique in its schema .

argmode

A parameter mode ：IN、OUT、 INOUT perhaps VARIADIC. If it's ignored , The default is IN. Be careful  DROP FUNCTION Don't really care about  OUT Parameters , Because you only need to input parameters to determine the identity of the function . So list IN、INOUT and  VARIADIC The parameters are sufficient .

argname

The name of a parameter . Be careful  DROP FUNCTION Don't really care about parameter names , Because only the data type of the parameter is needed to determine the identity of the function .

argtype

If the function has parameters , This is the data type of the function parameter （ It can be pattern Limited ）.

CASCADE

Automatically delete objects that depend on this function （ Such as operators and triggers ）, Then delete all objects that depend on those objects （ see   Rely on tracking  ）.

RESTRICT

If any object depends on this function , Then refuse to delete it . This is the default .

Example

This command removes the square root function ：

DROP FUNCTION sqrt(integer);

Delete multiple functions in one command ：

DROP FUNCTION sqrt(integer), sqrt(bigint);

If the function name is unique in its schema , You can reference it without a parameter list ：

DROP FUNCTION update_employee_salaries;

Please note that , This is related to 

DROP FUNCTION update_employee_salaries();

Different , The latter refers to a function with zero parameters , The first variant can refer to functions with any number of parameters , Including zero , As long as the name is unique .

Compatibility

This command complies with SQL standard , Use these KingbaseES Expand ：

  • This standard allows only one function to be deleted per command .

  • IF EXISTS Options

  • Can specify parameter mode and name

17.18. DROP GROUP

purpose

DROP GROUP — Remove a database role

DROP GROUP Now it is  DROP ROLE  An alias for .

precondition

See  DROP ROLE

grammar 

DROP GROUP [ IF EXISTS ] name [, ...]

semantics

IF EXISTS

Don't throw an error if the role doesn't exist , It's a reminder .

name

The name of the role to be removed .

Example 

DROP GROUP regress_priv_group1;

Compatibility

stay SQL There is no in the standard DROP GROUP sentence .

17.19. DROP INDEX

purpose

DROP INDEX Remove an existing index from the database system .

precondition

To execute this command, you must be the owner of the index .

grammar 

DROP INDEX [ CONCURRENTLY ] [ IF EXISTS ] name [, ...] [ CASCADE | RESTRICT ]

semantics

CONCURRENTLY

Delete the index without blocking the concurrent selection on the index base table 、 Insert 、 Update and delete operations . One ordinary DROP INDEX Will require the exclusive lock on the form , This will block Other accesses until the index deletion is completed . With this option , The command will wait until the conflicting transaction is completed .

There are some things to pay attention to when using this option . Only one index name can be specified , And don't support a CASCADE Options （ therefore , One support UNIQUE perhaps  PRIMARY KEY Constrained indexes cannot be deleted in this way ）. also , routine Of DROP INDEX Commands can be executed within a transaction block , and  DROP INDEX CONCURRENTLY You can't .

IF EXISTS

If the index does not exist, do not throw an error , It's a reminder .

name

The name of the index to be removed （ It can be pattern Limited ）.

CASCADE

Automatically delete objects that depend on the index , Then delete all objects that depend on those objects （ see   Rely on tracking  ）.

RESTRICT

If any object depends on the index , Then refuse to delete it . This is the default .

Example

This command will remove the index title_idx：

DROP INDEX title_idx;

Compatibility

DROP INDEX It's a KingbaseES Language extension . stay SQL There is no stipulation about index in the standard .

17.20. DROP LANGUAGE

purpose

DROP LANGUAGE — Remove a process language

DROP LANGUAGE Remove the definition of a previously registered process language .

precondition

You must be a super user or the owner of the language to use ``DROP LANGUAGE``.

grammar 

DROP [ PROCEDURAL ] LANGUAGE [ IF EXISTS ] name [ CASCADE | RESTRICT ]

semantics

IF EXISTS

Do not throw an error if the language does not exist , It's a reminder .

name

The name of an existing process language . For forward compatibility , This name can be enclosed in single quotation marks .

CASCADE

Automatically delete objects that depend on the language （ For example, functions in this language ）, Then delete all objects that depend on those objects （ see   Rely on tracking  ）.

RESTRICT

If any object depends on the language , Then refuse to delete it . This is the default .

Example

This command removes the process language plsample：

DROP LANGUAGE plsample;

Compatibility

stay SQL There is no in the standard DROP LANGUAGE sentence .

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