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https://github.com/ianmcook/queryparser

Translate SQL queries into R expressions
https://github.com/ianmcook/queryparser

database r sql tidyverse

Last synced: 9 days ago
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Translate SQL queries into R expressions

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README

        

---
output: github_document
---

```{r, include = FALSE}
knitr::opts_chunk$set(
collapse = TRUE,
comment = "#>",
fig.path = "man/figures/README-",
out.width = "100%"
)
```
# queryparser

[![CRAN status](https://www.r-pkg.org/badges/version/queryparser)](https://cran.r-project.org/package=queryparser)
[![Travis build status](https://travis-ci.com/ianmcook/queryparser.svg?branch=master)](https://travis-ci.com/ianmcook/queryparser)
[![AppVeyor build status](https://ci.appveyor.com/api/projects/status/github/ianmcook/queryparser?branch=master&svg=true)](https://ci.appveyor.com/project/ianmcook/queryparser)
[![Codecov test coverage](https://codecov.io/gh/ianmcook/queryparser/branch/master/graph/badge.svg)](https://codecov.io/gh/ianmcook/queryparser?branch=master)

**queryparser** translates SQL queries into lists of unevaluated R expressions.

| ⚠️ Most R users should not directly use queryparser. Instead, use it through [tidyquery](https://github.com/ianmcook/tidyquery).
| --- |

For an introduction to **tidyquery** and **queryparser**, watch the recording of the talk ["Bridging the Gap between SQL and R"](https://www.youtube.com/watch?v=JwP5KdWSgqE) from rstudio::conf(2020).

## Installation

Install the released version of **queryparser** from [CRAN](https://CRAN.R-project.org/package=queryparser) with:

``` r
install.packages("queryparser")
```

Or install the development version from [GitHub](https://github.com/ianmcook/queryparser) with:

``` r
# install.packages("remotes")
remotes::install_github("ianmcook/queryparser")
```

## Usage

Call the function `parse_query()`, passing a `SELECT` statement enclosed in quotes as the first argument:

```{r}
library(queryparser)

parse_query("SELECT DISTINCT carrier FROM flights WHERE dest = 'HNL'")
```

Queries can include the clauses `SELECT`, `FROM`, `WHERE`, `GROUP BY`, `HAVING`, `ORDER BY`, and `LIMIT`:

```{r}
parse_query(
" SELECT origin, dest,
COUNT(flight) AS num_flts,
round(SUM(seats)) AS num_seats,
round(AVG(arr_delay)) AS avg_delay
FROM flights f LEFT OUTER JOIN planes p
ON f.tailnum = p.tailnum
WHERE distance BETWEEN 200 AND 300
AND air_time IS NOT NULL
GROUP BY origin, dest
HAVING num_flts > 3000
ORDER BY num_seats DESC, avg_delay ASC
LIMIT 2;"
)
```

Set the argument `tidyverse` to `TRUE` to use functions from [tidyverse](https://www.tidyverse.org) packages including [dplyr](https://dplyr.tidyverse.org), [stringr](https://stringr.tidyverse.org), and [lubridate](https://lubridate.tidyverse.org) in the R expressions:

```{r}
parse_query("SELECT COUNT(*) AS n FROM t WHERE x BETWEEN y AND z ORDER BY n DESC", tidyverse = TRUE)
```

**queryparser** will translate only explicitly allowed functions and operators, preventing injection of malicious code:

```{r error=TRUE}
parse_query("SELECT x FROM y WHERE system('rm -rf /')")
```

## Current Limitations

**queryparser** does not currently support:

- Subqueries
- Unions
- SQL-89-style (implicit) join notation
- The `WITH` clause (common table expressions)
- `OVER` expressions (window or analytic functions)
- Some SQL functions and operators

**queryparser** currently has the following known limitations:

- Some SQL expressions will translate only when `tidyverse` is set to `TRUE`. An example of this is `COUNT(DISTINCT ...)` expressions with multiple arguments.
- When logical operators (such as `IS NULL`) have unparenthesized expressions as their operands, R will interpret the resulting code using a different order of operations than a SQL engine would. When using an expression as the operand to a logical operator, always enclose the expression in parentheses.
- The error messages that occur when attempting to parse invalid or unrecognized SQL are often non-informative.

## Non-Goals

**queryparser** is not intended to:

- Translate other types of SQL statements (such as `INSERT` or `UPDATE`)
- Customize translations for specific SQL dialects
- Fully validate the syntax of the `SELECT` statements passed to it
- Efficiently process large batches of queries
- Facilitate the analysis of queries (for example, to identify patterns)

## Related Work

The **sqlparseR** package ([CRAN](https://cran.r-project.org/package=sqlparseR)) provides a wrapper around the Python module **sqlparse**.