As defined in Chapter 19, SML# extends the Standard ML expressions with the following constructs for SQL queries:

$⟨$sql$\mathrm{⟩}$ and $⟨$sqlfn$\mathrm{⟩}$ are given below:

$⟨$sqlexp$\mathrm{⟩}$ is defined in Section 22.4. $⟨$sqlselect$\mathrm{⟩}$ and $⟨$sqcommand$\mathrm{⟩}$ are defined in Section 22.5. $⟨$sqlcommand$\mathrm{⟩}$ is defined in Section 22.6.

In the expressions that begins with _sql, except for the position surrounded by ...($\mathrm{⟨}$exp$\mathrm{⟩}$) or (...$\mathrm{⟨}$exp$\mathrm{⟩}$) (see Section 22.4, 22.5, and 22.6 for details), the following words are recognized as keywords (this list of keywords is reused from Section 17.2). In the sequel, the following words are refered to as SQL keywords.

asc all begin by commit cross default delete desc distinct fetch first from group inner insert into is join limit natural next not null offset only on or order rollback row rows select set update values where

The above syntax has the following limitations:

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  $⟨$pat$\mathrm{⟩}$ following _sql must not begin with a left parenthesize “(.”

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  The $⟨$sql$\mathrm{⟩}$ of _sql $\mathrm{⟨}$sql$\mathrm{⟩}$ as expressions (top-level) must begin with an SQL keyword.

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  Any _sql $\mathrm{⟨}$sql$\mathrm{⟩}$ as expressions (top-level) must occur only at the following positions:

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    the immediate right side of = in a val and fun declarations,

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    the position between in and end in a let expression,

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    the inside of a sequential execution expression ($\mathrm{\cdots }$;$\mathrm{\cdots }$),

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    immediately surrounded by parenthesizes that are not a part of any tuple, and

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    the immediate right side of => in a fn expression occurring at one of the above four positions.