honeysql/doc/special-syntax.md

SQL Special Syntax

This section lists the function-like expressions that HoneySQL supports out of the box which are formatted as special syntactic forms.

array

Accepts a single argument, which is expected to evaluate to a sequence, and produces ARRAY[?, ?, ..] for the elements of that sequence (as SQL parameters):

(sql/format-expr [:array (range 5)])
;;=> ["ARRAY[?, ?, ?, ?, ?]" 0 1 2 3 4]

between

Accepts three arguments: an expression, a lower bound, and an upper bound:

(sql/format-expr [:between :id 1 100])
;;=> ["id BETWEEN ? AND ?" 1 100]

case

A SQL CASE expression. Expects an even number of arguments: alternating condition and result expressions. A condition may be :else (or 'else) to produce ELSE, otherwise WHEN <condition> THEN <result> will be produced:

(sql/format-expr [:case [:< :a 10] "small" [:> :a 100] "big" :else "medium"])
;;=> ["CASE WHEN a < ? THEN ? WHEN a > ? THEN ? ELSE ? END"
;;    10 "small" 100 "big" "medium"]

cast

A SQL CAST expression. Expects an expression and something that produces a SQL type:

(sql/format-expr [:cast :a :int])
;;=> ["CAST(a AS int)"]

composite

Accepts any number of expressions and produces a composite expression (comma-separated, wrapped in parentheses):

(sql/format-expr [:composite :a :b "red" [:+ :x 1]])
;;=> ["(a, b, ?, x + ?)" "red" 1]

default

Takes no arguments and produces the SQL keyword DEFAULT.

[I expect this to be expanded for PostgreSQL]

inline

Accepts a single argument and tries to render it as a SQL value directly in the formatted SQL string rather than turning it into a positional parameter:

• nil becomes NULL
• keywords and symbols become upper case entities (with - replaced by space)
• strings become inline SQL strings (with single quotes)
• a sequence has each element formatted inline and then joined with spaces
• all other values are just rendered via Clojure's str function

(sql/format {:where [:= :x [:inline "foo"]]})
;;=> ["WHERE x = 'foo'"]

interval

Accepts two arguments: an expression and a keyword (or a symbol) that represents a time unit. Produces an INTERVAL expression:

(sql/format-expr [:date_add [:now] [:interval 30 :days]])
;;=> ["DATE_ADD(NOW(), INTERVAL ? DAYS)" 30]

lift

Used to wrap a Clojure value that should be passed as a SQL parameter but would otherwise be treated as a SQL expression or statement, i.e., a sequence or hash map. This can be useful when dealing with JSON types:

(sql/format {:where [:= :json-col [:lift {:a 1 :b "two"}]]})
;;=> ["WHERE json_col = ?" {:a 1 :b "two"}]

nest

Used to wrap an expression when you want an extra level of parentheses around it:

(sql/format {:where [:= :x 42]})
;;=> ["WHERE x = ?" 42]
(sql/format {:where [:nest [:= :x 42]]})
;;=> ["WHERE (x = ?)" 42]

nest is also supported as a SQL clause for the same reason.

not

Accepts a single expression and formats it with NOT in front of it:

(sql/format-expr [:not nil])
;;=> ["NOT NULL"]
(sql/format-expr [:not [:= :x 42]])
;;=> ["NOT x = ?" 42]

over

This is intended to be used with the :window and :partition-by clauses.

:over takes any number of window expressions which are either pairs or triples that have an aggregation expression, a window function, and an optional alias.

The window function may either be a SQL entity (named in a :window clause) or a SQL clause that describes the window (e.g., using :partition-by and/or :order-by).

Since a function call (using :over) needs to be wrapped in a sequence for a :select clause, it is usually easier to use the over helper function to construct this expression.

param

Used to identify a named parameter in a SQL expression as an alternative to a keyword (or a symbol) that begins with ?:

(sql/format {:where [:= :x :?foo]} {:params {:foo 42}})
;;=> ["WHERE x = ?" 42]
(sql/format {:where [:= :x [:param :foo]]} {:params {:foo 42}})
;;=> ["WHERE x = ?" 42]

raw

Accepts a single argument and renders it as literal SQL in the formatted string:

(sql/format {:select [:a [[:raw "@var := foo"]]]})
;;=> ["SELECT a, @var := foo"]

If the argument is a sequence of expressions, they will each be rendered literally and joined together (with no spaces):

(sql/format {:select [:a [[:raw ["@var" " := " "foo"]]]]})
;;=> ["SELECT a, @var := foo"]

When a sequence of expressions is supplied, any subexpressions that are, in turn, sequences will be formatted as regular SQL expressions and that SQL will be joined into the result, along with any parameters from them:

(sql/format {:select [:a [[:raw ["@var := " [:inline "foo"]]]]]})
;;=> ["SELECT a, @var := 'foo'"]
(sql/format {:select [:a [[:raw ["@var := " ["foo"]]]]]})
;;=> ["SELECT a, @var := ?" "foo"]