espresso_pgo_wrapper - v0.0.5

database/query

A query builder for Postgres, it’s not fully built out yet and currently only performs the most basic queries.

Types

Query

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A query is a struct that contains the schema to query from, the fields to select, the where clause, and the bindings for the query.

Normally you won’t interact with this struct directly, instead you’ll use the functions below to build up a query and then pass it to the associated functions to get the SQL string. These are already wrapped in the top level database module.

pub type Query(a) {
  Query(
    from: Schema(a),
    select: List(String),
    where: List(String),
    bindings: List(pgo.Value),
  )
}

Constructors 

  • Query(
  from: Schema(a),
  select: List(String),
  where: List(String),
  bindings: List(pgo.Value),
)

Where

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A where clause is a list of tuples where the first element is the field name and the second is the value to bind to that field. It will automatically generate the correct number of placeholders for the values and append them to the bindings list for PGO.

pub type Where =
  List(#(String, List(pgo.Value)))

Functions

build

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pub fn build(query: Query(a)) -> String

Builds the SQL string for the query. This is the same as SELECT ... FROM ... WHERE ... in SQL.

delete

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pub fn delete(query: Query(a)) -> String

Builds the SQL string for a delete query. This is the same as DELETE FROM ... WHERE ... in SQL. It will return the deleted rows.

from

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pub fn from(schema: Schema(a)) -> Query(a)

Create a new query from a schema. This is the starting point for building a query and the schema’s decoder is also used as the returned value.

insert

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pub fn insert(schema: Schema(a)) -> String

Builds the SQL string for an insert query. This is the same as INSERT INTO ... (field1, field2, ...) VALUES (value1, value2, ...) in SQL. It will ignore the primary key field in the schema but may supporrt that in the future.

select

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pub fn select(query: Query(a), fields: List(String)) -> Query(a)

Adds fields to the select clause of the query. This is the same as SELECT field1, field2, ... in SQL.

update

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pub fn update(query: Query(a), fields: List(#(String, Value))) -> String

Builds the SQL string for an update query. This is the same as UPDATE ... SET field1 = value1, field2 = value2, ... in SQL. It will return the updated rows.

where

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pub fn where(query: Query(a), bindings: List(
    #(String, List(Value)),
  )) -> Query(a)

Adds a where clause to the query. This is the same as WHERE field = value in SQL. The values will be appended to the bindings list for PGO.

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