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Database

#Database| 来源: 网络整理| 查看: 265

Constructor # new Database(data) Parameters: Name Type Description data Array.

An array of bytes representing an SQLite database file

Source: api.js, line 825 Methods # ["close"]()

Close the database, and all associated prepared statements. The memory associated to the database and all associated statements will be freed.

Warning: A statement belonging to a database that has been closed cannot be used anymore.

Databases must be closed when you're finished with them, or the memory consumption will grow forever

Source: api.js, line 1103 # ["create_aggregate"](name, aggregateFunctions) → {Database}

Parameters: Name Type Description name string

the name of the aggregate as referenced in SQL statements.

aggregateFunctions object

object containing at least a step function.

Properties Name Type Attributes Default Description init function ()=>null

a function receiving no arguments and returning an initial value for the aggregate function. The initial value will be null if this key is omitted.

step function

a function receiving the current state and a value to aggregate and returning a new state. Will receive the value from init for the first step.

finalize function (state)=>state

a function returning the result of the aggregate function given its final state. If omitted, the value returned by the last step will be used as the final value.

Source: api.js, line 1278 Returns:

The database object. Useful for method chaining

Type Database Example

db.create_aggregate("js_sum", { init: () => 0, step: (state, value) => state + value, finalize: state => state }); db.exec("SELECT js_sum(column1) FROM (VALUES (1), (2))"); // = 3 # ["create_function"](name, func) → {Database}

Parameters: Name Type Description name string

the name of the function as referenced in SQL statements.

func function

the actual function to be executed.

Source: api.js, line 1212 Returns:

The database object. Useful for method chaining

Type Database Example

db.create_function("addOne", function (x) {return x+1;}) db.exec("SELECT addOne(1)") // = 2 # ["each"](sql, paramsopt, callback, done) → {Database}

Execute an sql statement, and call a callback for each row of result.

Currently this method is synchronous, it will not return until the callback has been called on every row of the result. But this might change. Parameters: Name Type Attributes Default Description sql string

A string of SQL text. Can contain placeholders that will be bound to the parameters given as the second argument

params Statement.BindParams []

Parameters to bind to the query

callback function

Function to call on each row of result

done function

A function that will be called when all rows have been retrieved

Source: api.js, line 1011 Returns:

The database object. Useful for method chaining

Type Database Example

Read values from a table

db.each("SELECT name,age FROM users WHERE age >= $majority", {$majority:18}, function (row){console.log(row.name + " is a grown-up.")} ); # ["exec"](sql, paramsopt) → {Array.}

Execute an SQL query, and returns the result.

This is a wrapper against Database.prepare, Statement.bind, Statement.step, Statement.get, and Statement.free.

The result is an array of result elements. There are as many result elements as the number of statements in your sql string (statements are separated by a semicolon)

Example use

We will create the following table, named test and query it with a multi-line statement using params:

id age name 1 1 Ling 2 18 Paul

We query it like that:

var db = new SQL.Database(); var res = db.exec( "DROP TABLE IF EXISTS test;\n" + "CREATE TABLE test (id INTEGER, age INTEGER, name TEXT);" + "INSERT INTO test VALUES ($id1, :age1, @name1);" + "INSERT INTO test VALUES ($id2, :age2, @name2);" + "SELECT id FROM test;" + "SELECT age,name FROM test WHERE id=$id1", { "$id1": 1, ":age1": 1, "@name1": "Ling", "$id2": 2, ":age2": 18, "@name2": "Paul" } );

res is now :

[ {"columns":["id"],"values":[[1],[2]]}, {"columns":["age","name"],"values":[[1,"Ling"]]} ] Parameters: Name Type Attributes Description sql string

a string containing some SQL text to execute

params Statement.BindParams

When the SQL statement contains placeholders, you can pass them in here. They will be bound to the statement before it is executed. If you use the params argument as an array, you cannot provide an sql string that contains several statements (separated by ;). This limitation does not apply to params as an object.

Source: api.js, line 939 Returns:

The results of each statement

Type Array. # ["export"]() → {Uint8Array}

Exports the contents of the database to a binary array

Source: api.js, line 1080 Returns:

An array of bytes of the SQLite3 database file

Type Uint8Array # ["getRowsModified"]() → {number}

Returns the number of changed rows (modified, inserted or deleted) by the latest completed INSERT, UPDATE or DELETE statement on the database. Executing any other type of SQL statement does not modify the value returned by this function.

Source: api.js, line 1138 Returns:

the number of rows modified

Type number # ["handleError"]()

Analyze a result code, return null if no error occured, and throw an error with a descriptive message otherwise

Source: api.js, line 1122 # ["iterateStatements"](sql) → {StatementIterator}

Iterate over multiple SQL statements in a SQL string. This function returns an iterator over Statement objects. You can use a for..of loop to execute the returned statements one by one.

Parameters: Name Type Description sql string

a string of SQL that can contain multiple statements

Source: api.js, line 1073 Returns:

the resulting statement iterator

Type StatementIterator Example

Get the results of multiple SQL queries

Prepare an SQL statement

Parameters: Name Type Attributes Description sql string

a string of SQL, that can contain placeholders (?, :VVV, :AAA, @AAA)

params Statement.BindParams

values to bind to placeholders

Source: api.js, line 1041 Throws:

SQLite error

Type String Returns:

the resulting statement

Type Statement # ["run"](sql, paramsopt) → {Database}

Execute an SQL query, ignoring the rows it returns.

Parameters: Name Type Attributes Description sql string

a string containing some SQL text to execute

params Statement.BindParams

When the SQL statement contains placeholders, you can pass them in here. They will be bound to the statement before it is executed. If you use the params argument, you cannot provide an sql string that contains several statements (separated by ;)

Source: api.js, line 856 Returns:

The database object (useful for method chaining)

Type Database Example // Insert values in a table db.run( "INSERT INTO test VALUES (:age, :name)", { ':age' : 18, ':name' : 'John' } ); Type Definitions # QueryExecResult Type: Object Properties Name Type Description columns Array.

the name of the columns of the result (as returned by Statement.getColumnNames)

values Array.

one array per row, containing the column values

Source: api.js, line 873 # SqlValue Type: string | number | null | Uint8Array Source: api.js, line 280

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