R: Interpolate strings with SQL escaping

glue_sql {glue} | R Documentation

## Interpolate strings with SQL escaping

### Description

SQL databases often have custom quotation syntax for identifiers and strings which make writing SQL queries error prone and cumbersome to do. `glue_sql()` and `glue_sql_data()` are analogs to `glue()` and `glue_data()` which handle the SQL quoting.

### Usage

    glue_sql(..., .con, .envir = parent.frame())

    glue_data_sql(.x, ..., .con, .envir = parent.frame())

### Arguments

`...` | [`expressions`] Expressions string(s) to format, multiple inputs are concatenated together before formatting.
`.con` | [`DBIConnection`]:A DBI connection object obtained from `DBI::dbConnect()`.
`.envir` | [`environment`: `parent.frame()`] Environment to evaluate each expression in. Expressions are evaluated from left to right. If `.x` is an environment, the expressions are evaluated in that environment and `.envir` is ignored.
`.x` | [`listish`] An environment, list or data frame used to lookup values.

### Details

They automatically quote character results, quote identifiers if the glue expression is surrounded by backticks ‘'’ and do not quote non-characters such as numbers.

Returning the result with `DBI::SQL()` will suppress quoting if desired for a given value.

Note parameterized queries are generally the safest and most efficient way to pass user defined values in a query, however not every database driver supports them.

If you place a `*` at the end of a glue expression the values will be collapsed with commas. This is useful for the SQL IN Operator for instance.

### Value

A `DBI::SQL()` object with the given query.

### Examples

    con <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
    colnames(iris) <- gsub("[.]", "_", tolower(colnames(iris)))
    DBI::dbWriteTable(con, "iris", iris)
    var <- "sepal_width"
    tbl <- "iris"
    num <- 2
    val <- "setosa"
    glue_sql("
      SELECT {`var`}
      FROM {`tbl`}
      WHERE {`tbl`}.sepal_length > {num}
        AND {`tbl`}.species = {val}
      ", .con = con)

    # `glue_sql()` can be used in conjuction with parameterized queries using
    # `DBI::dbBind()` to provide protection for SQL Injection attacks
     sql <- glue_sql("
        SELECT {`var`}
        FROM {`tbl`}
        WHERE {`tbl`}.sepal_length > ?
      ", .con = con)
    query <- DBI::dbSendQuery(con, sql)
    DBI::dbBind(query, list(num))
    DBI::dbFetch(query, n = 4)
    DBI::dbClearResult(query)

    # `glue_sql()` can be used to build up more complex queries with
    # interchangeable sub queries. It returns `DBI::SQL()` objects which are
    # properly protected from quoting.
    sub_query <- glue_sql("
      SELECT *
      FROM {`tbl`}
      ", .con = con)

    glue_sql("
      SELECT s.{`var`}
      FROM ({sub_query}) AS s
      ", .con = con)

    # If you want to input multiple values for use in SQL IN statements put `*`
    # at the end of the value and the values will be collapsed and quoted appropriately.
    glue_sql("SELECT * FROM {`tbl`} WHERE sepal_length IN ({vals*})",
      vals = 1, .con = con)

    glue_sql("SELECT * FROM {`tbl`} WHERE sepal_length IN ({vals*})",
      vals = 1:5, .con = con)

    glue_sql("SELECT * FROM {`tbl`} WHERE species IN ({vals*})",
      vals = "setosa", .con = con)

    glue_sql("SELECT * FROM {`tbl`} WHERE species IN ({vals*})",
      vals = c("setosa", "versicolor"), .con = con)

    DBI::dbDisconnect(con)

[Package glue version 1.2.0 Index]