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Connection
Represents a single database connection from a pool of connections.
创建源
The DbPool.connection method. You do not call a connection constructor directly. Once you have a Connection object, you use it for your interactions with the database.
描述
You can use the prototype property of the Connection class to add a property to all Connection instances. If you do so, that addition applies to all Connection objects running in all applications on your server, not just in the single application that made the change. This allows you to expand the capabilities of this object for your entire server.
属性概览
方法概览
属性
prototype
Represents the prototype for this class. You can use the prototype to add properties or methods to all instances of a class. For information on prototypes, see Function.prototype.
方法
beginTransaction
Begins a new SQL transaction.
语法
beginTransaction()
参数
无。
返回
0 if the call was successful; otherwise, a nonzero status code based on any error message passed by the database. If the method returns a nonzero status code, use the associated majorErrorCode and majorErrorMessage methods to interpret the cause of the error.
描述
All subsequent actions that modify the database are grouped with this transaction, known as the current transaction.
For the database object, the scope of a transaction is limited to the current request (HTML page) in the application. If the application exits the page before calling the commitTransaction or rollbackTransaction method, then the transaction is automatically either committed or rolled back, based on the setting of the commitflag parameter when the connection was established. This parameter is provided when you make the connection by calling database.connect.
For Connection objects, the scope of a transaction is limited to the lifetime of that object. If the connection is released or the pool of connections is closed before calling the commitTransaction or rollbackTransaction method, then the transaction is automatically either committed or rolled back, based on the setting of the commitflag parameter when the connection was established. This parameter is provided when you make the connection by calling the connect method or in the DbPool constructor.
If there is no current transaction (that is, if the application has not called beginTransaction), calls to commitTransaction and rollbackTransaction are ignored.
The LiveWire Database Service does not support nested transactions. If you call beginTransaction when a transaction is already open (that is, you've called beginTransaction and have yet to commit or roll back that transaction), you'll get an error message.
示例
This example updates the rentals 表 within a transaction. The values of customerID and videoID are passed into the cursor method as properties of the request object. When the videoReturn Cursor object opens, the next method navigates to the only record in the answer set and updates the value in the returnDate field.
The variable x is assigned a database status code to indicate if the updateRow method is successful. If updateRow succeeds, the value of x is 0, and the transaction is committed; otherwise, the transaction is rolled back.
// Begin a transaction
database.beginTransaction();
// Create a Date object with the value of today's date
today = new Date();
// Create a Cursor with the rented video in the answer set
videoReturn = database.Cursor("SELECT * FROM rentals WHERE
customerId = " + request.customerID + " AND
videoId = " + request.videoID, true);
// Position the pointer on the first row of the Cursor
// and update the row
videoReturn.next()
videoReturn.returndate = today;
x = videoReturn.updateRow("rentals");
// End the transaction by committing or rolling back
if (x == 0) {
database.commitTransaction() }
else {
database.rollbackTransaction() }
// Close the Cursor
videoReturn.close();
commitTransaction
Commits the current transaction
语法
commitTransaction()
参数
无。
返回
0 if the call was successful; otherwise, a nonzero status code based on any error message passed by the database. If the method returns a nonzero status code, use the associated majorErrorCode and majorErrorMessage methods to interpret the cause of the error.
描述
This method attempts to commit all actions since the last call to beginTransaction.
For the database object, the scope of a transaction is limited to the current request (HTML page) in the application. If the application exits the page before calling the commitTransaction or rollbackTransaction method, then the transaction is automatically either committed or rolled back, based on the setting of the commitflag parameter when the connection was established. This parameter is provided when you make the connection with the database or DbPool object.
For Connection objects, the scope of a transaction is limited to the lifetime of that object. If the connection is released or the pool of connections is closed before calling the commitTransaction or rollbackTransaction method, then the transaction is automatically either committed or rolled back, based on the commitFlag value.
If there is no current transaction (that is, if the application has not called beginTransaction), calls to commitTransaction and rollbackTransaction are ignored.
The LiveWire Database Service does not support nested transactions. If you call beginTransaction when a transaction is already open (that is, you've called beginTransaction and have yet to commit or roll back that transaction), you'll get an error message.
connected
Tests whether the database pool and all of its connections are connected to a database.
语法
connected()
参数
无。
返回
True if the pool (and hence a particular connection in the pool) is currently connected to a database; otherwise, false.
描述
The connected method indicates whether this object is currently connected to a database.
If this method returns false for a Connection object, you cannot use any other methods of that object. You must reconnect to the database, using the DbPool object, and then get a new Connection object. Similarly, if this method returns false for the database object, you must reconnect before using other methods of that object.
示例
示例 1: The following code fragment checks to see if the connection is currently open. If it's not, it reconnects the pool and reassigns a new value to the myconn variable.
if (!myconn.connected()) {
mypool.connect ("INFORMIX", "myserver", "SYSTEM", "MANAGER", "mydb", 4);
myconn = mypool.connection;
}
示例 2: The following example uses an if condition to determine if an application is connected to a database server. If the application is connected, the isConnectedRoutine function runs; if the application is not connected, the isNotConnected routine runs.
if(database.connected()) {
isConnectedRoutine() }
else {
isNotConnectedRoutine() }
cursor
Creates a Cursor object.
语法
cursor("sqlStatement",upda表)
参数
返回
A new Cursor object.
描述
The cursor method creates a Cursor object that contains the rows returned by a SQL SELECT statement. The SELECT statement is passed to the cursor method as the sqlStatement argument. If the SELECT statement does not return any rows, the resulting Cursor object has no rows. The first time you use the next method on the object, it returns false.
You can perform the following tasks with the Cursor object:
The cursor method does not automatically display the returned data. To display this data, you must create custom HTML code. This HTML code may display the rows in an HTML 表, as shown in Example 3. The SQL表 method is an easier way to display the output of a database query, but you cannot navigate, modify data, or control the format of the output.
The optional parameter upda表 specifies whether you can modify the Cursor object you create with the cursor method. To create a Cursor object you can modify, specify upda表 as true. If you do not specify a value for the upda表 parameter, it is false by default.
If you create an upda表 Cursor object, the answer set returned by the sqlStatement parameter must be upda表. For example, the SELECT statement in the sqlStatement parameter cannot contain a GROUP BY clause; in addition, the query usually must retrieve key values from a 表. For more information on constructing upda表 queries, consult your database vendor's documentation.
示例
示例 1. The following example creates the upda表 cursor custs and returns the columns ID, CUST_NAME, and CITY from the customer 表:
custs = database.Cursor("select id, cust_name, city from customer", true)
示例 2. You can construct the SELECT statement with the string concatenation operator (+) and string variables such as client or request property values, as shown in the following example:
custs = database.Cursor("select * from customer
where customerID = " + request.customerID);
示例 3. The following example demonstrates how to format the answer set returned by the cursor method as an HTML 表. This example first creates Cursor object named videoSet and then displays two columns of its data (videoSet.title and videoSet.synopsis).
// Create the videoSet Cursor
<SERVER>
videoSet = database.cursor("select * from videos
where videos.numonhand > 0 order by title");
</SERVER>
// Begin creating an HTML 表 to contain the answer set
// Specify titles for the two columns in the answer set
<表 BORDER>
<CAPTION> Videos on Hand </CAPTION>
<TR>
<TH>Title</TH>
<TH>Synopsis</TH>
</TR>
// Use a while loop to iterate over each row in the cursor
<SERVER>
while(videoSet.next()) {
</SERVER>
// Use write statements to display the data in both columns
<TR>
<TH><A HREF=\Q"rent.html?videoID="+videoSet.id\Q>
<SERVER>write(videoSet.title)</SERVER></A></TH>
<TD><SERVER>write(videoSet.synopsis)</SERVER></TD>
</TR>
// End the while loop
<SERVER>
}
</SERVER>
// End the HTML 表
</表>
The values in the videoSet.title column are displayed within the A tag so a user can click them as links. When a user clicks a title, the rent.html page opens and the column value videoSet.id is passed to it as the value of request.videoID.
参看
Connection.SQL表, Connection.cursor
execute
Performs the specified SQL statement. Use for SQL statements other than queries.
语法
execute (stmt)
参数
返回
0 if the call was successful; otherwise, a nonzero status code based on any error message passed by the database. If the method returns a nonzero status code, use the associated majorErrorCode and majorErrorMessage methods to interpret the cause of the error.
描述
This method enables an application to execute any data definition language (DDL) or data manipulation language (DML) SQL statement supported by the database server that does not return a Cursor, such as CREATE, ALTER, or DROP.
Each database supports a standard core of DDL and DML statements. In addition, they may each also support DDL and DML statements specific to that database vendor. You can use execute to call any of those statements. However, each database vendor may also provide functions you can use with the database that are not DDL or DML statements. You cannot use execute to call those functions. For example, you cannot call the Oracle describe function or the Informix load function from the execute method.
Although technically you can use execute to perform data modification (INSERT, UPDATE, and DELETE statements), you should instead use Cursor objects. This makes your application more database-independent. Cursors also provide support for binary large object (BLOb) data.
When using the execute method, your SQL statement must strictly conform to the语法 requirements of the database server. For example, some servers require each SQL statement to be terminated by a semicolon. See your server documentation for more information.
If you have not explicitly started a transaction, the single statement is automatically committed.
示例
In the following example, the execute method is used to delete a customer from the customer 表. customer.ID represents the unique ID of a customer that is in the ID column of the customer 表. The value for customer.ID is passed into the DELETE statement as the value of the ID property of the request object.
if(request.ID != null) {
database.execute("delete from customer
where customer.ID = " + request.ID)
}
majorErrorCode
Major error code returned by the database server or ODBC.
语法
majorErrorCode()
参数
无。
返回
The result returned by this method depends on the database server being used:
描述
SQL statements can fail for a variety of reasons, including referential integrity constraints, lack of user privileges, record or 表 locking in a multiuser database, and so on. When an action fails, the database server returns an error message indicating the reason for failure. The LiveWire Database Service provides two ways of getting error information: from the status code returned by various methods or from special properties containing error messages and codes.
Status codes are integers between 0 and 27, with 0 indicating a successful execution of the statement and other numbers indicating an error, as shown in 表 10.4.
表 10.4 Database status codes.
示例
This example updates the rentals 表 within a transaction. The updateRow method assigns a database status code to the statusCode variable to indicate whether the method is successful.
If updateRow succeeds, the value of statusCode is 0, and the transaction is committed. If updateRow returns a statusCode value of either five or seven, the values of majorErrorCode, majorErrorMessage, minorErrorCode, and minorErrorMessage are displayed. If statusCode is set to any other value, the errorRoutine function is called.
database.beginTransaction()
statusCode = cursor.updateRow("rentals")
if (statusCode == 0) {
database.commitTransaction()
}
if (statusCode == 5 || statusCode == 7) {
write("The operation failed to complete.<BR>"
write("Contact your system administrator with the following:<P>"
write("The value of statusCode is " + statusCode + "<BR>")
write("The value of majorErrorCode is " +
database.majorErrorCode() + "<BR>")
write("The value of majorErrorMessage is " +
database.majorErrorMessage() + "<BR>")
write("The value of minorErrorCode is " +
database.minorErrorCode() + "<BR>")
write("The value of minorErrorMessage is " +
database.minorErrorMessage() + "<BR>")
database.rollbackTransaction()
}
else {
errorRoutine()
}
majorErrorMessage
Major error message returned by database server or ODBC. For server errors, this typically corresponds to the server's SQLCODE.
语法
majorErrorMessage()
参数
无。
返回
A string describing that depends on the database server:
描述
SQL statements can fail for a variety of reasons, including referential integrity constraints, lack of user privileges, record or 表 locking in a multiuser database, and so on. When an action fails, the database server returns an error message indicating the reason for failure. The LiveWire Database Service provides two ways of getting error information: from the status code returned by connection and DbPool methods or from special connection or DbPool properties containing error messages and codes.
示例
See Connection.majorErrorCode.
minorErrorCode
Secondary error code returned by database vendor library.
语法
minorErrorCode()
参数
无。
返回
The result returned by this method depends on the database server:
minorErrorMessage
Secondary message returned by database vendor library.
语法
minorErrorMessage()
参数
无。
返回
The string returned by this method depends on the database server:
release
Releases the connection back to the database pool.
语法
release()
参数
无。
返回
0 if the call was successful; otherwise, a nonzero status code based on any error message passed by the database. If the method returns a nonzero status code, use the associated majorErrorCode and majorErrorMessage methods to interpret the cause of the error.
描述
Before calling the release method, you should close all open cursors. When you call the release method, the runtime engine waits until all cursors have been closed and then returns the connection to the database pool. The connection is then available to the next user.
If you don't call the release method, the connection remains unavailable until the object goes out of scope. Assuming the object has been assigned to a variable, it can go out of scope at different times:
You must call the release method for all connections in a database pool before you can call the DbPool object's disconnect method. Otherwise, the connection is still considered in use by the runtime engine, so the disconnect waits until all connections are released.
rollbackTransaction
Rolls back the current transaction.
语法
rollbackTransaction()
参数
无。
返回
0 if the call was successful; otherwise, a nonzero status code based on any error message passed by the database. If the method returns a nonzero status code, use the associated majorErrorCode and majorErrorMessage methods to interpret the cause of the error.
描述
This method will undo all modifications since the last call to beginTransaction.
For the database object, the scope of a transaction is limited to the current request (HTML page) in the application. If the application exits the page before calling the commitTransaction or rollbackTransaction method, then the transaction is automatically either committed or rolled back, based on the setting of the commitflag parameter when the connection was established. This parameter is provided when you make the connection with the database or DbPool object.
For Connection objects, the scope of a transaction is limited to the lifetime of that object. If the connection is released or the pool of connections is closed before calling the commitTransaction or rollbackTransaction method, then the transaction is automatically either committed or rolled back, based on the commitFlag value.
If there is no current transaction (that is, if the application has not called beginTransaction), calls to commitTransaction and rollbackTransaction are ignored.
The LiveWire Database Service does not support nested transactions. If you call beginTransaction when a transaction is already open (that is, you've called beginTransaction and have yet to commit or roll back that transaction), you'll get an error message.
SQL表
Displays query results. Creates an HTML 表 for results of an SQL SELECT statement.
语法
SQL表 (stmt)
参数
返回
A string representing an HTML 表, with each row and column in the query as a row and column of the 表.
描述
Although SQL表 does not give explicit control over how the output is formatted, it is the easiest way to display query results. If you want to customize the appearance of the output, use a Cursor object to create your own display function.
Note
Every Sybase 表 you use with a cursor must have a unique index.
示例
If connobj is a Connection object and request.sql contains an SQL query, then the following JavaScript statements display the result of the query in a 表:
write(request.sql)
connobj.SQL表(request.sql)
The first line simply displays the SELECT statement, and the second line displays the results of the query. This is the first part of the HTML generated by these statements:
select * from videos
<表 BORDER>
<TR>
<TH>title</TH>
<TH>id</TH>
<TH>year</TH>
<TH>category</TH>
<TH>quantity</TH>
<TH>numonhand</TH>
<TH>synopsis</TH>
</TR>
<TR>
<TD>A Clockwork Orange</TD>
<TD>1</TD>
<TD>1975</TD>
<TD>Science Fiction</TD>
<TD>5</TD>
<TD>3</TD>
<TD> Little Alex, played by Malcolm Macdowell,
and his droogies stop by the Miloko bar for a
refreshing libation before a wild night on the town.
</TD>
</TR>
<TR>
<TD>Sleepless In Seattle</TD>
...
As this example illustrates, SQL表 generates an HTML 表, with column headings for each column in the database 表 and a row in the 表 for each row in the database 表.
storedProc
Creates a stored-procedure object and runs the specified stored procedure.
语法
storedwProc (procName, inarg1, inarg2, ..., inargN)
参数
返回
A new Stproc object.
描述
The scope of the stored-procedure object is a single page of the application. In other words, all methods to be executed for any instance of storedProc must be invoked on the same application page as the page on which the object is created.
When you create a stored procedure, you can specify default values for any of
the parameters. Then, if a parameter is not included when the stored procedure
is executed, the procedure uses the default value. However, when you call a
stored procedure from a server-side JavaScript application, you must indicate
that you want to use the default value by typing "/Default/" in place of the
parameter. (Remember that JavaScript is case sensitive.) For example:
spObj = connobj.storedProc ("newhire", "/Default/", 3)
toString
Returns a string representing the specified object.
语法
toString()
参数
无。
描述
Every object has a toString method that is automatically called when it is to be represented as a text value or when an object is referred to in a string concatenation.
You can use toString within your own code to convert an object into a string, and you can create your own function to be called in place of the default toString method.
This method returns a string of the following format:
db "name" "userName" "dbtype" "serverName"
where
The method displays an empty string for any of attributes whose value is unknown.
For information on defining your own toString method, see the Object.toString method.
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