Gbase 8C - SQL reference 6 SQL syntax (4)

1. ALTER TYPE

Function description

Modify parameters of type .

Grammar format

ALTER TYPE name action [, ... ]

ALTER TYPE name OWNER TO { new_owner | CURRENT_USER | SESSION_USER }

ALTER TYPE name RENAME ATTRIBUTE attribute_name TO new_attribute_name [ CASCADE | RESTRICT ]

ALTER TYPE name RENAME TO new_name

ALTER TYPE name SET SCHEMA new_schema

ALTER TYPE name ADD VALUE [ IF NOT EXISTS ] new_enum_value [ { BEFORE | AFTER } neighbor_enum_value ]

ALTER TYPE name RENAME VALUE existing_enum_value TO new_enum_value

here action Is one of the following ：

    ADD ATTRIBUTE attribute_name data_type [ COLLATE collation ] [ CASCADE | RESTRICT ]

    DROP ATTRIBUTE [ IF EXISTS ] attribute_name [ CASCADE | RESTRICT ]

    ALTER ATTRIBUTE attribute_name [ SET DATA ] TYPE data_type [ COLLATE collation ] [ CASCADE | RESTRICT ]

Parameter description

1. name： The name of the existing type that needs to be modified , Can be modified by patterns ;
2. new_name： New name of this type ;
3. new_owner： User name of the new owner ;
4. new_schema： New mode of this type ;
5. attribute_name： To add 、 Name of the changed or deleted attribute ;
6. new_attribute_name： The new name of the attribute to be renamed ;
7. data_type： The data type of the attribute to be added , Or the new type name of the attribute to be changed ;
8. new_enum_value： Enumeration type new tag value , Need to be quoted in quotation marks ;
9. neighbor_enum_value： An existing enumeration tag value , The new value should be added immediately before or after the enumeration value ;
10. existing_enum_value： Existing enumeration value to rename , Need to be quoted in quotation marks ;
11. CASCADE： Automatic cascading updates require updating types, associated records, and child tables that inherit them ;
12. RESTRICT： If the type of linkage update is the associated record of the updated type , Then refuse to update , This is the default option ;

matters needing attention

Use ALTER TYPE Must be the owner of this type .

Example

ALTER TYPE compfoo RENAME TO g_compfoo;

ALTER TYPE

Grammar compatible

ALTER TYPE Adding and deleting are SQL Belong to SQL standard , Other parameters are PostgreSQL Expand .

Related to the grammar

CREATE TYPE, DROP TYPE

1. ALTER USER

Function description

Modify the attributes of database users .

Grammar format

ALTER USER role_specification [ WITH ] option [ ... ]

among option It can be ：

      SUPERUSER | NOSUPERUSER

    | CREATEDB | NOCREATEDB

    | CREATEROLE | NOCREATEROLE

    | INHERIT | NOINHERIT

    | LOGIN | NOLOGIN

    | REPLICATION | NOREPLICATION

    | BYPASSRLS | NOBYPASSRLS

    | CONNECTION LIMIT connlimit

    | [ ENCRYPTED ] PASSWORD 'password'

    | VALID UNTIL 'timestamp'

ALTER USER name RENAME TO new_name

ALTER USER { role_specification | ALL } [ IN DATABASE database_name ] SET configuration_parameter { TO | = } { value | DEFAULT }

ALTER USER { role_specification | ALL } [ IN DATABASE database_name ] SET configuration_parameter FROM CURRENT

ALTER USER { role_specification | ALL } [ IN DATABASE database_name ] RESET configuration_parameter

ALTER USER { role_specification | ALL } [ IN DATABASE database_name ] RESET ALL

among role_specification It can be ：

    role_name

  | CURRENT_USER

  | SESSION_USER

matters needing attention

ALTER USER Now it is ALTER ROLE An alias for . See ALTER ROLE.

Grammar compatible

ALTER USER Sentence is a kind of PostgreSQL Expand .

Related to the grammar

CREATE USER, DROP USER, ALTER ROLE

1. ALTER VIEW

Function description

Change various auxiliary properties of the view .

Grammar format

ALTER VIEW [ IF EXISTS ] name ALTER [ COLUMN ] column_name SET DEFAULT expression

ALTER VIEW [ IF EXISTS ] name ALTER [ COLUMN ] column_name DROP DEFAULT

ALTER VIEW [ IF EXISTS ] name OWNER TO { new_owner | CURRENT_USER | SESSION_USER }

ALTER VIEW [ IF EXISTS ] name RENAME TO new_name

ALTER VIEW [ IF EXISTS ] name SET SCHEMA new_schema

ALTER VIEW [ IF EXISTS ] name SET ( view_option_name [= view_option_value] [, ... ] )

ALTER VIEW [ IF EXISTS ] name RESET ( view_option_name [, ... ] )

Parameter description

1. name： Existing view name , Can be decorated with patterns ;
2. IF EXISTS： If the view does not exist, no error will be reported , Just prompt ;
3. SET/DROP DEFAULT： Set or delete the default value of a column ;
4. new_owner： User name of the new owner of the view ;
5. new_name： New name of the view ;
6. new_schema： New mode of view ;
7. SET ( view_option_name [= view_option_value] [, ... ] ) | RESET ( view_option_name [, ... ] )： Specify an optional parameter for the view , Parameters can be chosen ：
   1. check_option (string)： Change the check options of the view , The optional value is local perhaps cascaded;
   2. security_barrier (boolean)： Specify view row level security ;

matters needing attention

To use ALTER VIEW Must be the owner of this view .

To change the mode of the view , Users must have new models CREATE jurisdiction .

To change the owner of the view , The user must be a direct or indirect member of the new role , And this role must have view mode CREATE jurisdiction .

The administrator user can change the ownership of any view .

Example

ALTER VIEW g_view RENAME TO gc_view;

ALTER VIEW

Grammar compatible

ALTER VIEW It's a kind of PostgreSQL Of SQL Standard extension .

Related to the grammar

CREATE VIEW, DROP VIEW

1. ANALYZE

Function description

It is used to collect statistical information related to the contents of common tables in the database .

Grammar format

ANALYZE [ VERBOSE ] [ table_name [ ( column_name [, ...] ) ] ]

Parameter description

1. VERBOSE： Enable the display of progress information ;
2. table_name： The table name of the specific table that needs to be analyzed （ May bring the mode name ）, If omitted , All tables in the database （ Except external table ） Analyze ;
3. column_name： You need to analyze the column names of specific columns , Default to all columns .

matters needing attention

If no parameter is specified ,ANALYZE It will analyze each table and partition table in the current database .

Example

ANALYZE VERBOSE orders;

INFO:  analyzing "public.orders" inheritance tree

INFO:  analyzing "public.orders_history"

INFO:  analyzing "public.orders_202003"

INFO:  analyzing "public.orders_202004"

ANALYZE

Grammar compatible

SQL There is no in the standard ANALYZE sentence .

Related to the grammar

VACUUM, EXPLAIN

1. BEGIN

Function description

BEGIN Used to start a transaction .

Grammar format

BEGIN [ WORK | TRANSACTION ] [ transaction_mode [, ...] ]

among transaction_mode Is one of the following ：

    ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED }

    READ WRITE | READ ONLY

    [ NOT ] DEFERRABLE

Parameter description

1. WORK | TRANSACTION： Optional keywords , It does nothing but increase readability .

For the meanings of other parameters, please refer to SET TRANSACTION.

matters needing attention

START TRANSACTION With and BEGIN Same function .

Use COMMIT perhaps ROLLBACK To terminate a transaction block .

Issued when already in a transaction block BEGIN Will trigger a warning , At this time, the transaction status will not be affected . To nest transactions in a transaction block , You can use a savepoint （SAVEPOINT）.

Due to backward compatibility , Successive transaction_modes The comma between can be omitted .

Example

Start a transaction ：

BEGIN;

Grammar compatible

BEGIN yes PostgreSQL Language extension , Equivalent to SQL The standard START TRANSACTION.

Related to the grammar

COMMIT, ROLLBACK, END, START TRANSACTION, SAVEPOINT

1. CHECKPOINT

Function description

checkpoint （CHECKPOINT） Is a point in the transaction log , All data files are updated at this point to reflect the information in the log , All data files will be flushed to disk .

Set transaction log checkpoints . Pre written logs （WAL） By default, a checkpoint is placed in the transaction log at intervals .

Grammar format

CHECKPOINT

matters needing attention

Only system administrators can call CHECKPOINT.

CHECKPOINT In the local CN And all DN Execution on node .

Example

CHECKPOINT;

CHECKPOINT

Grammar compatible

CHECKPOINT Command is a kind of PostgreSQL Language extension .

1. CLEAN CONNECTION

Function description

When there are exceptions in the database , Used to clean up database connections .

Grammar format

CLEAN CONNECTION TO { COORDINATOR ( nodename [, ... ] ) | NODE ( nodename [, ... ] ) | ALL {FORCE} }

    [ FOR DATABASE dbname ]

    [ TO USER username ]

Parameter description

1. FORCE： Only when the node list is TO ALL You can specify , If this parameter is specified , Before cleaning up the connection, it will check whether the database is accessed by other session connections , This parameter is mainly used for DROP DATABASE Previous connection access check , If other session connections are found , Will report an error and stop deleting the database ;
2. dbname： Delete the connection on the specified database , If not specified, delete the connection of all databases ;
3. username： Delete the connection on the specified user , If not specified, delete all users' connections ;
4. nodename： Delete the connection on the specified node , Three scenarios ：
   1. Delete the specified CN Connections on ;
   2. Delete the specified DN When connecting on , You need to specify the DN Group name ;
   3. Delete connections on all nodes , Include CN and DN.

Example

CLEAN CONNECTION TO ALL FORCE FOR DATABASE gbase TO USER gbase1;

CLEAN CONNECTION

CLEAN CONNECTION TO NODE (dn2) TO USER gbase1;

CLEAN CONNECTION

Grammar compatible

CLEAN CONNECTION Do not conform to the SQL standard

1. CLOSE

Function description

Release all resources associated with a cursor .

Grammar format

CLOSE { name | ALL }

matters needing attention

When creating cursor transactions COMMIT or ROLLBACK After the termination , Every open cursor that cannot be held is implicitly closed .

When the transaction that creates the cursor passes ROLLBACK After you quit , Every cursor that can be held will be closed implicitly .

GBase 8c No cursor is explicitly opened OPEN sentence , Because a cursor is in use CURSOR It opens when the command is defined . You can query the system view pg_cursors See all available cursors .

Grammar compatible

CLOSE Completely obey SQL standard .CLOSE ALL It's a kind of PostgreSQL Expand .

Related to the grammar

DECLARE, FETCH, MOVE

1. CLUSTER

Function description

Cluster and sort the table according to an index .

Grammar format

CLUSTER [VERBOSE] table_name [ USING index_name ]

CLUSTER [VERBOSE]

Parameter description

1. table_name： The name of the table , Can be modified by patterns ;
2. index_name： The index name ;
3. VERBOSE： Print progress report when clustering the table .

matters needing attention

Only line deposit B-tree Index support CLUSTER operation .

If the user just randomly accesses the rows in the table , Then the actual storage order of the data in the table is irrelevant . however , If some data is accessed more than others , And there is an index that groups these data , So it's going to use CLUSTER Will help . If you request the value of a certain index range from a table , Or one index value corresponds to multiple rows ,CLUSTER It will also help to apply , Because if the index identifies the storage page where the first matching row is located , All other rows may already be in the same storage page , This saves disk access time , Speed up queries .

During clustering , The system first creates a temporary copy of the table established according to the index order . It also creates a temporary copy of each index on the table . therefore , You need enough free space on the disk , At least the sum of table size and index size .

because CLUSTER Memory gathers information , You can cluster tables manually for the first time , Then set a similar VACUUM Time for , In this way, the table can be automatically clustered periodically .

Because the optimizer records statistics about the sorting of tables , Therefore, it is recommended to run on the newly clustered table ANALYZE. otherwise , The optimizer may choose poor Query Planning .

CLUSTER It is not allowed to execute .

CLUSTER Will also be performed on all data nodes .

Example

CLUSTER customer USING gcustomer_idx;

CLUSTER

Grammar compatible

stay SQL There is no in the standard CLUSTER sentence .

1. COMMENT

Function description

Define or modify the annotation of an object .

Grammar format

COMMENT ON

{

  ACCESS METHOD object_name |

  AGGREGATE aggregate_name ( aggregate_signature ) |

  CAST (source_type AS target_type) |

  COLLATION object_name |

  COLUMN relation_name.column_name |

  CONSTRAINT constraint_name ON table_name |

  CONSTRAINT constraint_name ON DOMAIN domain_name |

  CONVERSION object_name |

  DATABASE object_name |

  DOMAIN object_name |

  EXTENSION object_name |

  EVENT TRIGGER object_name |

  FOREIGN DATA WRAPPER object_name |

  FOREIGN TABLE object_name |

  FUNCTION function_name ( [ [ argmode ] [ argname ] argtype [, ...] ] ) |

  INDEX object_name |

  LARGE OBJECT large_object_oid |

  MATERIALIZED VIEW object_name |

  OPERATOR operator_name (left_type, right_type) |

  OPERATOR CLASS object_name USING index_method |

  OPERATOR FAMILY object_name USING index_method |

  POLICY policy_name ON table_name |

  [ PROCEDURAL ] LANGUAGE object_name |

  ROLE object_name |

  RULE rule_name ON table_name |

  SCHEMA object_name |

  SEQUENCE object_name |

  SERVER object_name |

  TABLE object_name |

  TABLESPACE object_name |

  TEXT SEARCH CONFIGURATION object_name |

  TEXT SEARCH DICTIONARY object_name |

  TEXT SEARCH PARSER object_name |

  TEXT SEARCH TEMPLATE object_name |

  TRANSFORM FOR type_name LANGUAGE lang_name |

  TRIGGER trigger_name ON table_name |

  TYPE object_name |

  VIEW object_name

} IS 'text'

  ACCESS METHOD object_name |

  AGGREGATE aggregate_name ( aggregate_signature ) |

  CAST (source_type AS target_type) |

  COLLATION object_name |

  COLUMN relation_name.column_name |

  CONSTRAINT constraint_name ON table_name |

  CONSTRAINT constraint_name ON DOMAIN domain_name |

  CONVERSION object_name |

  DATABASE object_name |

  DOMAIN object_name |

  EXTENSION object_name |

  EVENT TRIGGER object_name |

  FOREIGN DATA WRAPPER object_name |

  FOREIGN TABLE object_name |

  FUNCTION function_name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ] |

  INDEX object_name |

  LARGE OBJECT large_object_oid |

  MATERIALIZED VIEW object_name |

  OPERATOR operator_name (left_type, right_type) |

  OPERATOR CLASS object_name USING index_method |

  OPERATOR FAMILY object_name USING index_method |

  POLICY policy_name ON table_name |

  [ PROCEDURAL ] LANGUAGE object_name |

  PUBLICATION object_name |

  ROLE object_name |

  RULE rule_name ON table_name |

  SCHEMA object_name |

  SEQUENCE object_name |

  SERVER object_name |

  STATISTICS object_name |

  SUBSCRIPTION object_name |

  TABLE object_name |

  TABLESPACE object_name |

  TEXT SEARCH CONFIGURATION object_name |

  TEXT SEARCH DICTIONARY object_name |

  TEXT SEARCH PARSER object_name |

  TEXT SEARCH TEMPLATE object_name |

  TRANSFORM FOR type_name LANGUAGE lang_name |

  TRIGGER trigger_name ON table_name |

  TYPE object_name |

  VIEW object_name

} IS 'text'

among aggregate_signature yes ：

* |

[ argmode ] [ argname ] argtype [ , ... ] |

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

Parameter description

1. object_name： Object name ;
2. relation_name.column_name： Definition / Modify the column name of the comment , Prefix with table name ;
3. aggregate_name： The name of the aggregate function ;
4. constraint_name： Definition / Modify the name of the annotated table constraint ;
5. function_name： Definition / Modify the function name of the annotation ;
6. operator_name： Operator name ;
7. policy_name： Security policy name ;
8. rule_name： Rule name ;
9. trigger_name： Trigger Name .
10. table_name： The name of the table
11. domain_name： When in a constraint 、 trigger 、 When creating a comment on a rule or policy , These parameters specify the name of the table or field on which the object is defined
12. source_type： Source data type of type conversion ;
13. target_type： Target data type of type conversion ;
14. argmode： Mode of function parameters , Optional parameters ：IN、 OUT、INOUT perhaps VARIADIC, The default is IN;
15. argname： The name of the function parameter ;
16. argtype： The type of function argument ;
17. large_object_oid： Definition / Modify the annotation of large objects OID value ;
18. left_type | right_type： Data type of operation parameter , Can be modified by patterns , When the pre or post operator does not exist , Can increase NONE Options ;
19. PROCEDURAL： Noise words ;
20. type_name： The name of the data type to be converted ;
21. lang_name： The name of the language to be converted ;
22. text： notes .

matters needing attention

Currently, there is no security mechanism for annotation browsing ： Any user connected to a database can see all the comments of the database object . Shared objects （ Like databases 、 role 、 Table space ） Comments for are stored globally , Any user connected to any database can see them . therefore , Do not store sensitive information related to security in comments .

Example

COMMENT ON TABLE customer IS 'This is my customer.';

COMMENT

Grammar compatible

SQL There is no in the standard COMMENT command .