# PostgreSQL 函数

## 注释

> 注意:

> Not all functions are supported by all builds. It depends on your libpq (The PostgreSQL C client library) version and how libpq is compiled. If PHP PostgreSQL extensions are missing, then it is because your libpq version does not support them.

> 注意:

> Most PostgreSQL functions accept `connection` as the optional first parameter. If it is not provided, the last opened connection is used. If it doesn't exist, functions return `false`.

> 注意:

> PostgreSQL automatically folds all identifiers (e.g. table/column names) to lower-case values at object creation time and at query time. To force the use of mixed or upper case identifiers, you must escape the identifier using double quotes ("").

> 注意:

> PostgreSQL does not have special commands for fetching database schema information (eg. all the tables in the current database). Instead, there is a standard schema named `information_schema` in PostgreSQL 7.4 and above containing system views with all the necessary information, in an easily queryable form. See the » PostgreSQL Documentation for full details.

## 目录

- pg_affected_rows — 返回受影响的记录数（元组）
- pg_cancel_query — 取消异步查询
- pg_client_encoding — 获取客户端编码
- pg_close — 关闭 PostgreSQL 连接
- pg_connect — 打开 PostgreSQL 连接
- pg_connect_poll — 对正在进行尝试进行异步的 PostgreSQL 连接轮询其状态。
- pg_connection_busy — 获取连接是否繁忙
- pg_connection_reset — 重置连接（再次连接）
- pg_connection_status — 获取连接状态
- pg_consume_input — Reads input on the connection
- pg_convert — 将关联的数组值转换为适合 SQL 语句的格式
- pg_copy_from — 将数组中的记录插入到表
- pg_copy_to — 将表复制到数组
- pg_dbname — 获取数据库名称
- pg_delete — 删除记录
- pg_end_copy — 与 PostgreSQL 后端同步
- pg_escape_bytea — 转义字符串以插入到 bytea 字段
- pg_escape_identifier — Escape a identifier for insertion into a text field
- pg_escape_literal — Escape a literal for insertion into a text field
- pg_escape_string — 转义字符串以供查询
- pg_execute — Sends a request to execute a prepared statement with given parameters, and waits for the result
- pg_fetch_all — 从结果中获取所有行作为数组
- pg_fetch_all_columns — Fetches all rows in a particular result column as an array
- pg_fetch_array — 获取一行作为数组
- pg_fetch_assoc — 获取一行作为关联数组
- pg_fetch_object — 获取一行作为对象
- pg_fetch_result — 从结果实例返回值
- pg_fetch_row — 提取一行作为枚举数组
- pg_field_is_null — 测试字段是否为 SQL NULL
- pg_field_name — 返回字段名
- pg_field_num — 返回名为 field 的字段编号
- pg_field_prtlen — 返回打印的长度
- pg_field_size — 返回指定字段的内部存储大小
- pg_field_table — Returns the name or oid of the tables field
- pg_field_type — 返回相应字段编号的类型名称
- pg_field_type_oid — Returns the type ID (OID) for the corresponding field number
- pg_flush — 刷新链接中已处理的数据查询
- pg_free_result — 释放查询结果占用的内存
- pg_get_notify — 获取 SQL NOTIFY 消息
- pg_get_pid — 获取后端的进程 ID
- pg_get_result — 取得异步查询结果
- pg_host — 返回和某连接关联的主机名
- pg_insert — 将数组插入到表中
- pg_last_error — 得到某连接的最后一条错误信息
- pg_last_notice — 返回 PostgreSQL 服务器最新一条公告信息
- pg_last_oid — 返回上一条记录的 oid
- pg_lo_close — 关闭大对象
- pg_lo_create — 新建大对象
- pg_lo_export — 将大型对象导出到文件
- pg_lo_import — 将文件导入为大型对象
- pg_lo_open — 打开大对象
- pg_lo_read — 读取大对象
- pg_lo_read_all — 读取整个大对象并直接发送到浏览器
- pg_lo_seek — 在大对象中寻找位置
- pg_lo_tell — 返回当前大型对象的指针位置
- pg_lo_truncate — Truncates a large object
- pg_lo_unlink — 删除一个大型对象
- pg_lo_write — 向大对象写入数据
- pg_meta_data — 获得表的元数据
- pg_num_fields — 返回结果中字段的数量
- pg_num_rows — 返回结果中行的数量
- pg_options — 获得和 connection 相关的选项
- pg_parameter_status — Looks up a current parameter setting of the server
- pg_pconnect — 打开一个持久的 PostgreSQL 连接
- pg_ping — Ping 数据库连接
- pg_port — 返回 connection 相关的端口号
- pg_prepare — Submits a request to the server to create a prepared statement with the given parameters, and waits for completion
- pg_put_line — 向 PostgreSQL 后端发送以 NULL 字符结尾的字符串
- pg_query — 执行查询
- pg_query_params — Submits a command to the server and waits for the result, with the ability to pass parameters separately from the SQL command text
- pg_result_error — 获得跟 result 相关的错误信息
- pg_result_error_field — Returns an individual field of an error report
- pg_result_memory_size — Returns the amount of memory allocated for a query result
- pg_result_seek — 在 result 实例中设定内部行偏移量
- pg_result_status — 获得查询结果的状态
- pg_select — 选择记录
- pg_send_execute — Sends a request to execute a prepared statement with given parameters, without waiting for the result(s)
- pg_send_prepare — Sends a request to create a prepared statement with the given parameters, without waiting for completion
- pg_send_query — 发送异步查询
- pg_send_query_params — Submits a command and separate parameters to the server without waiting for the result(s)
- pg_set_chunked_rows_size — Set the query results to be retrieved in chunk mode
- pg_set_client_encoding — 设定客户端编码
- pg_set_error_context_visibility — Determines the visibility of the context's error messages returned by pg_last_error and pg_result_error
- pg_set_error_verbosity — Determines the verbosity of messages returned by pg_last_error and pg_result_error
- pg_socket — Get a read only handle to the socket underlying a PostgreSQL connection
- pg_trace — 启用 PostgreSQL 连接的追踪
- pg_transaction_status — Returns the current in-transaction status of the server
- pg_tty — 返回跟连接相关的 tty 名
- pg_unescape_bytea — 反转义 bytea 类型的二进制数据
- pg_untrace — 禁用 PostgreSQL 连接的追踪
- pg_update — 更新表
- pg_version — Returns an array with client, protocol and server version (when available)

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