awSQL/docs/docusaurus/docs/classes/select.md

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Select

Performs a query to retrieve data from a table.

Methods

selectDatabase()

→ (database = String) → this

Selects a different database for this query.

Parameters

Parameter	Type	Description
database	String	Name of the database to select

Returns

→ this

---

distinct()

→ () → this

Adds the 'distinct' keyword to this query.

• With 'distinct' only unique values are returned

Returns

→ this

Example

Scenario: We want to get the EmployeeIDs of the Employees that have open orders in Orders

const empOrders = await instance.select("Orders", "EmployeeID") // Select table "Orders" and column "EmployeeID"
                                .distinct()                     // Only get unique EmployeeIDs
                                .execute();
console.log(empOrders);
/*
[
    RowDataPacket { EmployeeID: 5 },
    RowDataPacket { EmployeeID: 6 },
    RowDataPacket { EmployeeID: 4 },
    RowDataPacket { EmployeeID: 3 },
    RowDataPacket { EmployeeID: 9 },
    RowDataPacket { EmployeeID: 1 },
    RowDataPacket { EmployeeID: 8 },
    RowDataPacket { EmployeeID: 2 },
    RowDataPacket { EmployeeID: 7 }
]
*/

---

where()

→ (string = String, values = Array<any>) → this

Adds a where-clause to the query

• Values should be set as ? in the string and given in left-to-right order via the 'values'-array to minimize the risk of sql-injection
• If you are using joins, specify the table and column together: table.column

Parameters

Parameter	Type	Description
string	String	The where-clause as a string with ? representing each values.
values	Array<any>	Array containing values replacing the ? in the string (from left to right)

Returns

→ this

Example

Scenario: We only want to get the Orders from the Customers with the id 90 and 34

const filteredOrders = await instance.select("Orders")  // Select table 'Orders'
// Filter by orders where CustomerID are our desired ids.
// Note that the values of ? are pushed in order into the value-array
                                     .where("CustomerID = ? OR CustomerID = ?", [90, 34])
                                     .execute();
console.log(filteredOrders);
/*
[
  RowDataPacket {
    OrderID: 10248,
    CustomerID: 90,
    EmployeeID: 5,
    OrderDate: '1996-07-04',
    ShipperID: 3
  },
  RowDataPacket {
    OrderID: 10250,
    CustomerID: 34,
    EmployeeID: 4,
    OrderDate: '1996-07-08',
    ShipperID: 2
  },
  RowDataPacket {
    OrderID: 10253,
    CustomerID: 34,
    EmployeeID: 3,
    OrderDate: '1996-07-10',
    ShipperID: 2
  }
]
*/

---

having()

→ (string = String, values = Array<any>) → this

Same as where() but allows for aggregation.

• Values should be set as ? in the string and given in left-to-right order via the 'values'-array to minimize the risk of sql-injection
• If you are using joins, specify the table and column together: table.column

Parameters

Parameter	Type	Description
string	String	The having-clause with possible aggregation ? representing each values.
values	Array<any>	Array containing values replacing the ? in the string (from left to right)

Returns

→ this

---

order()

→ (column = String, desc = Boolean, aggregation = Enum) → this

Adds a new sort order.

• Can be used multiple times to order by multiple columns

Parameters

Parameter	Type	Description
column	String	Column to order by
desc	Boolean	Sort descending? Defaults to false
aggregation	Enum → MIN/MAX/COUNT/SUM/AVG	The aggregation type to use

Returns

→ this

---

count()

→ (doParse = Boolean) → this

Counts the number of entries of the first selected column.

Parameters

Parameter	Type	Description
doParse	Boolean	If true the query will only return a Number of entries. Defaults to false.

Returns

→ this

---

sum()

→ (doParse = Boolean) → this

Sums numerical rows of the first selected column.

Parameters

Parameter	Type	Description
doParse	Boolean	If true the query will only return a Number of entries. Defaults to false.

Returns

→ this

---

avg()

→ (doParse = Boolean) → this

Averages numerical rows of the first selected column.

Parameters

Parameter	Type	Description
doParse	Boolean	If true the query will only return a Number of entries. Defaults to false.

Returns

→ this

---

group()

→ (...columns = String) → this

Groups rows that have the same values into summary rows.

Parameters

Parameter	Type	Description
...columns	String	The columns to group by

Returns

→ this

---

join()

→ (type = Enum, table = String, onOriginalColumn = String, onJoinedColumn = String, ...columns = String) → this

Adds a new join to the query.

Parameters

Parameter	Type	Description
type	Enum → LEFT/INNER/RIGHT/FULL OUTER	The join type
table	String	Table to join on
onOriginalColumn	String	Column name on the original table to check agains
onJoinedColumn	String	Column name of the join table to check against
...columns	String	The columns to join. OG-columns must be set!

Returns

→ this

---

limit()

→ (number = Number, offset = Number) → this

Limits the query and specifies an offset to start at.

:::warning offset has no default value and therefore must not be empty! :::

Parameters

Parameter	Type	Description
number	Number	Limits the query by specified rows
offset	Number	Offset to start at.

Returns

→ this

---

pagination()

→ (page = Number, itemsPerPage = Number) → this

Paginates the query.

Parameters

Parameter	Type	Description
page	Number	The page to get (Minimum 1)
itemsPerPage	Number	How many items a page should have

Returns

→ this

---

execute()

async → () → any

Executes the prepared query.

Returns

→ any - Query result

---