openGauss高级特性：附录：SQL语法（7）

CALL

可以调用已定义的函数和存储过程。

CALL [schema.] func_name ( param_expr );

CHECKPOINT

检查点（CHECKPOINT）是一个事务日志中的点，所有数据文件都在该点被更新以反映日志中的信息，所有数据文件都将被刷新到磁盘。

CHECKPOINT

CLEAN CONNECTION

用来清理数据库连接。允许在节点上清理指定数据库的指定用户的相关连接。

CLEAN CONNECTION
    TO { COORDINATOR ( nodename [, ... ] ) | NODE ( nodename [, ... ] ) | ALL [ CHECK ] [ FORCE ] }
    [ FOR DATABASE dbname ]
    [ TO USER username ];

CLOSE

释放和一个游标关联的所有资源。

CLOSE { cursor_name | ALL };

CLUSTER

根据一个索引对表进行聚簇排序。

CLUSTER [ VERBOSE ] table_name [ USING index_name ];
CLUSTER [ VERBOSE ] table_name PARTITION ( partition_name ) [ USING index_name ];
CLUSTER [ VERBOSE ];

COMMENT

定义或修改一个对象的注释。

COMMENT ON
{
  AGGREGATE agg_name (agg_type [, ...] ) |
  CAST (source_type AS target_type) |
  COLLATION object_name |
  COLUMN { table_name.column_name | view_name.column_name } |
  CONSTRAINT constraint_name ON table_name |
  CONVERSION object_name |
  DATABASE object_name |
  DOMAIN object_name |
  EXTENSION 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 |
  OPERATOR operator_name (left_type, right_type) |
  OPERATOR CLASS object_name USING index_method |
  OPERATOR FAMILY object_name USING index_method |
  [ PROCEDURAL ] LANGUAGE object_name |
  ROLE object_name |
  RULE rule_name ON table_name |
  SCHEMA 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 |
  TYPE object_name |
  VIEW object_name
}
   IS 'text';

COMMIT

通过COMMIT或者END可完成提交事务的功能，即提交事务的所有操作。

{ COMMIT | END } [ WORK | TRANSACTION ];

COMMIT PREPARED

提交一个早先为两阶段提交准备好的事务。

COMMIT PREPARED transaction_id;

COPY

通过COPY命令实现在表和文件之间拷贝数据。

COPY table_name [ ( column_name [, ...] ) ]
    FROM { 'filename' | STDIN }
    [ [ USING ] DELIMITERS 'delimiters' ]
    [ WITHOUT ESCAPING ]
    [ LOG ERRORS ]
    [ LOG ERRORS DATA ]
    [ REJECT LIMIT 'limit' ]
    [ [ WITH ] ( option [, ...] ) ]
    | copy_option
    | [ FIXED FORMATTER ( { column_name( offset, length ) } [, ...] ) ]
    | [ TRANSFORM ( { column_name [ data_type ] [ AS transform_expr ] } [, ...] ) ];
COPY table_name [ ( column_name [, ...] ) ]
    TO { 'filename' | STDOUT }
    [ [ USING ] DELIMITERS 'delimiters' ]
    [ WITHOUT ESCAPING ]
    [ [ WITH ] ( option [, ...] ) ]
    | copy_option
    | [ FIXED FORMATTER ( { column_name( offset, length ) } [, ...] ) ];
COPY query
    TO { 'filename' | STDOUT }
    [ WITHOUT ESCAPING ]
    [ [ WITH ] ( option [, ...] ) ]
    | copy_option
    | [ FIXED FORMATTER ( { column_name( offset, length ) } [, ...] ) ];

where option can be:
FORMAT 'format_name'
| OIDS [ boolean ]
| DELIMITER 'delimiter_character'
| NULL 'null_string'
| HEADER [ boolean ]
| FILEHEADER 'header_file_string'
| FREEZE [ boolean ]
| QUOTE 'quote_character'
| ESCAPE 'escape_character'
| EOL 'newline_character'
| NOESCAPING [ boolean ]
| FORCE_QUOTE { ( column_name [, ...] ) | * }
| FORCE_NOT_NULL ( column_name [, ...] )
| FORCE_NULL ( column_name [, ...] )
| ENCODING 'encoding_name'
| IGNORE_EXTRA_DATA [ boolean ]
| FILL_MISSING_FIELDS [ boolean ]
| COMPATIBLE_ILLEGAL_CHARS [ boolean ]
| DATE_FORMAT 'date_format_string'
| TIME_FORMAT 'time_format_string'
| TIMESTAMP_FORMAT 'timestamp_format_string'
| SMALLDATETIME_FORMAT 'smalldatetime_format_string'

and copy_option can be:
OIDS
| NULL 'null_string'
| HEADER
| FILEHEADER 'header_file_string'
| FREEZE
| FORCE NOT NULL column_name [, ...]
| FORCE NULL column_name [, ...]
| FORCE QUOTE { column_name [, ...] | * }
| BINARY
| CSV
| QUOTE [ AS ] 'quote_character'
| ESCAPE [ AS ] 'escape_character'
| EOL 'newline_character'
| ENCODING 'encoding_name'
| IGNORE_EXTRA_DATA
| FILL_MISSING_FIELDS
| COMPATIBLE_ILLEGAL_CHARS
| DATE_FORMAT 'date_format_string'
| TIME_FORMAT 'time_format_string'
| TIMESTAMP_FORMAT 'timestamp_format_string'
| SMALLDATETIME_FORMAT 'smalldatetime_format_string'