rbql

    0.20.1 • Public • Published

    RBQL is both a library and a command line tool which provides SQL-like language with JavaScript expressions

    Table of Contents

    1. RBQL as browser library
    2. RBQL as Node library
    3. RBQL as command line tool
    4. RBQL language description

    Using RBQL as a browser library

    Installation:

    In order to make RBQL work in browser as a library for your App you need just one single file: rbql.js To get it you can either use npm:

    $ npm install rbql
    

    Now you can just source rbql.js and it will work:

    <script src="rbql.js"></script>
    

    API description

    The following two functions are avilable in the browser version:

    1. rbql.query_table(...)
    2. rbql.query(...)

    rbql.query_table(...)

    Run user query against input array of records and put the result set in the output array:

    async function query_table(user_query, input_table, output_table, output_warnings, join_table=null, input_column_names=null, join_column_names=null, output_column_names=null, normalize_column_names=true)
    

    Parameters:

    • user_query: string
      query that user of your app manually enters in some kind of input field.
    • input_table: array
      an array with input records
    • output_table: array
      an array where to output records would be pushed
    • output_warnings: array
      Warnings will be stored here after the query completion. If no warnings - the array would be empty
    • join_table: array
      an array with join table records so that user can use join table B in input queries
    • input_column_names: array
      Names of input_table columns which users of the app can use in their queries
    • join_column_names: array
      Names of join_table columns which users of the app can use in their queries
    • output_column_names: array
      Output column names will be stored in this array after the query completion.
    • normalize_column_names: boolean
      If set to true - column names provided with input_column_names and join_column_names will be normalized to "a" and "b" prefix forms e.g. "Age" -> "a.Age", "Sale price" -> "b['Sale price']".
      If set to false - column names can be used in user queries "as is".

    rbql.query(...)

    Allows to run queries against any kind of structured data.
    You will have to implement special wrapper classes for your custom data structures and pass them to the rbql.query(...) function.

    async function query(user_query, input_iterator, output_writer, output_warnings, join_tables_registry=null)
    

    Parameters:

    • user_query: string
      query that user of your app manually enters in some kind of input field.
    • input_iterator: RBQLInputIterator
      special object which iterates over input records. E.g. over a remote table Examples of classes which support RBQLInputIterator interface: TableIterator, CSVRecordIterator (these classes can be found in RBQL source code)
    • output_writer: RBQLOutputWriter
      special object which stores output records somewhere. E.g. to an array
      Examples of classes which support RBQLOutputWriter interface: TableWriter, CSVWriter (these classes can be found in RBQL source code)
    • output_warnings: array
      Warnings will be stored here after the query completion. If no warnings - the array would be empty
    • join_tables_registry: RBQLJoinTableRegistry
      special object which provides RBQLInputIterator iterators for join tables (e.g. table "B") which user can refer to in their queries.
      Examples of classes which support RBQLJoinTableRegistry interface: SingleTableRegistry, FileSystemCSVRegistry (these classes can be found in RBQL source code)

    Usage:

    "Hello world" web test in RBQL

    Very simple test to make sure that RBQL library works:

    <!DOCTYPE html>
    <html><head>
    <script src="../../rbql-js/rbql.js"></script>
    <script>
        let output_table = [];
        let warnings = [];
        let error_handler = function(exception) {
            console.log('RBQL finished with error: ' + String(exception));
        }
        let success_handler = function() {
            console.log('warnings: ' + JSON.stringify(warnings));
            console.log('output table: ' + JSON.stringify(output_table));
        }
        rbql.query_table('select a2 + " test", a1 limit 2', [[1, 'foo'], [2, 'bar'], [3, 'hello']], output_table, warnings).then(success_handler).catch(error_handler);
    </script>
    <title>RBQL Generic Test</title>
    </head><body>
    <div><span>Open browser console</span></div>
    </body></html>
    

    Save the code above as rbql_test.html; put rbql.js in the same folder; open rbql_test.html in your browser and make sure that console output contains the expected result.

    "JSFiddle" demo test

    A little more advanced, but still very simple demo test with JSFiddle It uses the same rbql.js script file.

    Using RBQL as Node library

    Installation:

    $ npm install rbql
    

    API description

    The following 3 functions are avilable in Node version:

    1. rbql.query_csv(...)
    2. rbql.query_table(...) - identical to browser version
    3. rbql.query(...) - identical to browser version

    rbql.query_csv(...)

    Run user query against input_path CSV file and save it as output_path CSV file.

    async function rbql.query_csv(user_query, input_path, input_delim, input_policy, output_path, output_delim, output_policy, csv_encoding, output_warnings, with_headers=false, comment_prefix=null)
    

    Parameters:

    • user_query: string
      query that user of your application manually enters in some kind of input field.
    • input_path: string
      path of the input csv table
    • input_delim: string
      field separator character in input table
    • input_policy: string
      allowed values: 'simple', 'quoted'
      along with input_delim defines CSV dialect of input table. "quoted" means that separator can be escaped inside double quoted fields
    • output_path: string
      path of the output csv table
    • output_delim: string
      same as input_delim but for output table
    • output_policy: string
      same as input_policy but for output table
    • csv_encoding: string
      allowed values: 'binary', 'utf-8'
      encoding of input, output and join tables (join table can be defined inside the user query)
    • output_warnings: array
      Warnings will be stored here after the query completion. If no warnings - the array would be empty
    • with_headers: boolean
      If set to true treat the first records in input (and join) file as header.
    • comment_prefix: string
      Treat lines starting with the prefix as comments and skip them.

    Usage:

    Example of query_table() usage:

    const rbql = require('rbql')
    let input_table = [
        ['Roosevelt',1858,'USA'],
        ['Napoleon',1769,'France'],
        ['Dmitri Mendeleev',1834,'Russia'],
        ['Jane Austen',1775,'England'],
        ['Hayao Miyazaki',1941,'Japan'],
    ];
    let user_query = 'SELECT a1, a2 % 1000 WHERE a3 != "USA" LIMIT 3';
    let output_table = [];
    let warnings = [];
    let error_handler = function(exception) {
        console.log('Error: ' + String(exception));
    }
    let success_handler = function() {
        console.log('warnings: ' + JSON.stringify(warnings));
        console.log('output table: ' + JSON.stringify(output_table));
    }
    rbql.query_table(user_query, input_table, output_table, warnings).then(success_handler).catch(error_handler);
    

    Example of query_csv() usage:

    const rbql_csv = require('rbql_csv');
    let user_query = 'SELECT a1, parseInt(a2) % 1000 WHERE a3 != "USA" LIMIT 5';
    let error_handler = function(exception) {
        console.log('Error: ' + String(exception));
    }
    let warnings = [];
    let success_handler = function() {
        if (warnings.length)
            console.log('warnings: ' + JSON.stringify(warnings));
        console.log('output table: output.csv');
    }
    rbql_csv.query_csv(user_query, 'input.csv', ',', 'quoted', 'output.csv', ',', 'quoted', 'utf-8', warnings).then(success_handler).catch(error_handler);
    

    You can also check rbql-js cli app code as a usage example: rbql-js cli source code

    Using RBQL as command line tool

    Installation:

    To use RBQL as CLI app you need to install it in global (-g) mode:

    $ npm install -g rbql
    

    Usage (non-interactive mode):

    $ rbql-js --query "select a1, a2 order by a1" < input.tsv
    

    Usage (interactive mode):

    In interactive mode rbql-js will show input table preview so it is easier to type SQL-like query.

    $ rbql-js --input input.csv --output result.csv
    

    Language description

    Main Features

    • Use JavaScript expressions inside SELECT, UPDATE, WHERE and ORDER BY statements
    • Supports multiple input formats
    • Result set of any query immediately becomes a first-class table on its own
    • No need to provide FROM statement in the query - input table is defined by the current context
    • Supports all main SQL keywords
    • Supports aggregate functions and GROUP BY queries
    • Supports user-defined functions (UDF)
    • Provides some new useful query modes which traditional SQL engines do not have
    • Lightweight, dependency-free, works out of the box

    Limitations:

    • RBQL doesn't support nested queries, but they can be emulated with consecutive queries
    • Number of tables in all JOIN queries is always 2 (input table and join table), use consecutive queries to join 3 or more tables

    Supported SQL Keywords (Keywords are case insensitive)

    • SELECT
    • UPDATE
    • WHERE
    • ORDER BY ... [ DESC | ASC ]
    • [ LEFT | INNER ] JOIN
    • DISTINCT
    • GROUP BY
    • TOP N
    • LIMIT N

    All keywords have the same meaning as in SQL queries. You can check them online

    RBQL variables

    RBQL for CSV files provides the following variables which you can use in your queries:

    • a1, a2,..., a{N}
      Variable type: string
      Description: value of i-th field in the current record in input table
    • b1, b2,..., b{N}
      Variable type: string
      Description: value of i-th field in the current record in join table B
    • NR
      Variable type: integer
      Description: Record number (1-based)
    • NF
      Variable type: integer
      Description: Number of fields in the current record
    • a.name, b.Person_age, ... a.{Good_alphanumeric_column_name}
      Variable type: string
      Description: Value of the field referenced by it's "name". You can use this notation if the field in the header has a "good" alphanumeric name
    • a["object id"], a['9.12341234'], b["%$ !! 10 20"] ... a["Arbitrary column name!"]
      Variable type: string
      Description: Value of the field referenced by it's "name". You can use this notation to reference fields by arbitrary values in the header

    UPDATE statement

    UPDATE query produces a new table where original values are replaced according to the UPDATE expression, so it can also be considered a special type of SELECT query. This prevents accidental data loss from poorly written queries.
    UPDATE SET is synonym to UPDATE, because in RBQL there is no need to specify the source table.

    Aggregate functions and queries

    RBQL supports the following aggregate functions, which can also be used with GROUP BY keyword:
    COUNT, ARRAY_AGG, MIN, MAX, SUM, AVG, VARIANCE, MEDIAN

    Limitation: aggregate functions inside JavaScript expressions are not supported. Although you can use expressions inside aggregate functions.
    E.g. MAX(float(a1) / 1000) - valid; MAX(a1) / 1000 - invalid.
    There is a workaround for the limitation above for ARRAY_AGG function which supports an optional parameter - a callback function that can do something with the aggregated array. Example:
    select a2, ARRAY_AGG(a1, v => v.sort().slice(0, 5)) group by a2

    JOIN statements

    Join table B can be referenced either by its file path or by its name - an arbitrary string which the user should provide before executing the JOIN query.
    RBQL supports STRICT LEFT JOIN which is like LEFT JOIN, but generates an error if any key in the left table "A" doesn't have exactly one matching key in the right table "B".
    Limitation: JOIN statements can't contain JavaScript expressions and must have the following form: <JOIN_KEYWORD> (/path/to/table.tsv | table_name ) ON a... == b... [AND a... == b... [AND ... ]]

    SELECT EXCEPT statement

    SELECT EXCEPT can be used to select everything except specific columns. E.g. to select everything but columns 2 and 4, run: SELECT * EXCEPT a2, a4
    Traditional SQL engines do not support this query mode.

    UNNEST() operator

    UNNEST(list) takes a list/array as an argument and repeats the output record multiple times - one time for each value from the list argument.
    Example: SELECT a1, UNNEST(a2.split(';'))

    LIKE() function

    RBQL does not support LIKE operator, instead it provides "like()" function which can be used like this: SELECT * where like(a1, 'foo%bar')

    WITH (header) and WITH (noheader) statements

    You can set whether the input (and join) CSV file has a header or not using the environment configuration parameters which could be --with_headers CLI flag or GUI checkbox or something else. But it is also possible to override this selection directly in the query by adding either WITH (header) or WITH (noheader) statement at the end of the query. Example: select top 5 NR, * with (header)

    User Defined Functions (UDF)

    RBQL supports User Defined Functions
    You can define custom functions and/or import libraries in a special file: ~/.rbql_init_source.js

    Examples of RBQL queries

    • select top 100 a1, a2 * 10, a4.length where a1 == "Buy" order by parseInt(a2) desc
    • select * order by Math.random() - random sort
    • select top 20 a.vehicle_price.length / 10, a2 where parseInt(a.vehicle_price) < 500 && ["car", "plane", "boat"].indexOf(a['Vehicle type']) > -1 limit 20 - referencing columns by names from header
    • update set a3 = 'NPC' where a3.indexOf('Non-playable character') != -1
    • select NR, * - enumerate records, NR is 1-based
    • select a1, b1, b2 inner join ./countries.txt on a2 == b1 order by a1, a3 - example of join query
    • select MAX(a1), MIN(a1) where a.Name != 'John' group by a2, a3 - example of aggregate query
    • select ...a1.split(':') - Using JS "destructuring assignment" syntax to split one column into many. Do not try this with other SQL engines!

    References

    Install

    npm i rbql

    Homepage

    rbql.org

    DownloadsWeekly Downloads

    3

    Version

    0.20.1

    License

    MIT

    Unpacked Size

    136 kB

    Total Files

    8

    Last publish

    Collaborators

    • mechatroner