如何从 CSV 为 PostgreSQL 副本生成模式

如果CSV不是太大，并且在本地机器上可用，那么csvkit是最简单的解决方案.它还包含许多用于处理CSV的其他实用程序，因此一般来说，这是一个需要了解的基础知识.

在shell中输入最简单的内容:

$ csvsql myfile.csv

将打印出所需的CREATE TABLE SQL命令，该命令可以使用输出重定向保存到文件中.

如果您还提供了连接字符串，csvsql将一次性创建表并上传文件:

$ csvsql --db "$MY_DB_URI" --insert myfile.csv

还有一些选项可以指定正在使用的SQL和CSV的风格.它们记录在内置帮助中:

$ csvsql -h
usage: csvsql [-h] [-d DELIMITER] [-t] [-q QUOTECHAR] [-u {0,1,2,3}] [-b]
              [-p ESCAPECHAR] [-z MAXFIELDSIZE] [-e ENCODING] [-S] [-H] [-v]
              [--zero] [-y SNIFFLIMIT]
              [-i {access,sybase,sqlite,informix,firebird,mysql,oracle,maxdb,postgresql,mssql}]
              [--db CONNECTION_STRING] [--query QUERY] [--insert]
              [--tables TABLE_NAMES] [--no-constraints] [--no-create]
              [--blanks] [--no-inference] [--db-schema DB_SCHEMA]
              [FILE [FILE ...]]

Generate SQL statements for one or more CSV files, create execute those
statements directly on a database, and execute one or more SQL queries.
positional arguments:
  FILE                  The CSV file(s) to operate on. If omitted, will accept
                        input on STDIN.

optional arguments:
  -h, --help            show this help message and exit
  -d DELIMITER, --delimiter DELIMITER
                        Delimiting character of the input CSV file.
  -t, --tabs            Specifies that the input CSV file is delimited with
                        tabs. Overrides "-d".
  -q QUOTECHAR, --quotechar QUOTECHAR
                        Character used to quote strings in the input CSV file.
  -u {0,1,2,3}, --quoting {0,1,2,3}
                        Quoting style used in the input CSV file. 0 = Quote
                        Minimal, 1 = Quote All, 2 = Quote Non-numeric, 3 =
                        Quote None.
  -b, --doublequote     Whether or not double quotes are doubled in the input
                        CSV file.
  -p ESCAPECHAR, --escapechar ESCAPECHAR
                        Character used to escape the delimiter if --quoting 3
                        ("Quote None") is specified and to escape the
                        QUOTECHAR if --doublequote is not specified.
  -z MAXFIELDSIZE, --maxfieldsize MAXFIELDSIZE
                        Maximum length of a single field in the input CSV
                        file.
  -e ENCODING, --encoding ENCODING
                        Specify the encoding the input CSV file.
  -S, --skipinitialspace
                        Ignore whitespace immediately following the delimiter.
  -H, --no-header-row   Specifies that the input CSV file has no header row.
                        Will create default headers.
  -v, --verbose         Print detailed tracebacks when errors occur.
  --zero                When interpreting or displaying column numbers, use
                        zero-based numbering instead of the default 1-based
                        numbering.
  -y SNIFFLIMIT, --snifflimit SNIFFLIMIT
                        Limit CSV dialect sniffing to the specified number of
                        bytes. Specify "0" to disable sniffing entirely.
  -i {access,sybase,sqlite,informix,firebird,mysql,oracle,maxdb,postgresql,mssql}, --dialect {access,sybase,sqlite,informix,firebird,mysql,oracle,maxdb,postgresql,mssql}
                        Dialect of SQL to generate. Only valid when --db is
                        not specified.
  --db CONNECTION_STRING
                        If present, a sqlalchemy connection string to use to
                        directly execute generated SQL on a database.
  --query QUERY         Execute one or more SQL queries delimited by ";" and
                        output the result of the last query as CSV.
  --insert              In addition to creating the table, also insert the
                        data into the table. Only valid when --db is
                        specified.
  --tables TABLE_NAMES  Specify one or more names for the tables to be
                        created. If omitted, the filename (minus extension) or
                        "stdin" will be used.
  --no-constraints      Generate a schema without length limits or null
                        checks. Useful when sampling big tables.
  --no-create           Skip creating a table. Only valid when --insert is
                        specified.
  --blanks              Do not coerce empty strings to NULL values.
  --no-inference        Disable type inference when parsing the input.
  --db-schema DB_SCHEMA
                        Optional name of database schema to create table(s)
                        in.

其他几种工具也可以进行模式推断，包括:

• apache 星火
• Pandas (Python )
• 布莱泽(Python )
• 阅读csv+你最喜欢的R数据库包

每一个都具有将CSV(和其他格式)读入表格数据 struct (通常称为DataFrame或类似 struct )的功能，从而推断过程中的列类型.然后，他们可以使用其他命令来写出等效的SQL模式，或者直接将数据帧上传到指定的数据库中.工具的 Select 将取决于数据量、存储方式、CSV的特性、目标数据库和您喜欢使用的语言.