#include <SQLDBC.h>
Definition at line 598 of file SQLDBC.h.
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Returns the number of columns in this ResultSet object.
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Returns maximum width in characters of the specified column.
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Requests the name of the specified column.
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Returns the data type of the specified column.
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Returns column's maximum physical width in bytes of the specified columns.
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Returns the maximum number of decimal digits of the specified column. For number types, getPrecision retrieves the number of decimal digits. For character types, it retrieves the maximum length in characters. For binary types, it retrieves the maximum length in bytes.
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Returns the number of decimal places of the data type of the specified column. For non-numeric types, the scale is set to zero.
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Returns whether NULL values are allowed for the specified column values.
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Returns whether a write operation is possible on the specified column.
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A class for preparing and executing SQL statements. A prepared SQL command can be parsed and contain input and output parameters. Parameters are marked with a '?' or ':<name>' tag. All DML commands can be parsed. DDL commands can be parsed, too. However, it is not recommended to do so. Prepared SQL commands increase the performance since they are parsed only once and executed several times. Applications only need to change the content of the bound parameters and execute the command again. All prepared SQL commands are stored in an internally managed ParseInfo Cache . The ParseInfo Cache shares this information with different prepared SQL statements within the same connection.
The SQL statement may contain ASCII or UCS2 characters and must not zero-terminated. The execute() member function converts it to the adequate code set considering the code of the database. Therefore it is possible to write portable code for UNICODE and non-UNICODE databases.
SQLDBC_PrepareStatement *stmt = conn->createPreparedStatement(); SQLDBC_Retcode rc = stmt->prepare("SELECT * FROM DUAL"); if (rc != SQLDBC_OK) { // Handle error ... } rc = stmt->execute(); if (rc != SQLDBC_OK) { // Handle error ... }
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A class for presenting a database result set. A database result set is generated by executing an SQL statement that queries the database. Select statements, catalog functions, and some procedures create result sets. For example, the following SQL statement creates a result set containing all the rows and columns of the table DUAL:
A result set can be empty, which is different from there being no result set at all. For example, the following SQL statement creates an empty result set:
An SQLDBC_ResultSet object maintains a cursor pointing to its current row of data. Initially the cursor is positioned before the first row. The next() method moves the cursor to the next row, and as it returns SQLDBC_NO_DATA_FOUND when there are no more rows in the SQLDBC_ResultSet object, it can be used in a WHILE loop to iterate the result set. Example for creating an SQLDBC_ResultSet object:
To reduce the time needed for retrieving the data from the database, the SQLDBC_ResultSet class supports so called block cursors, which can return more than one row at a time. The rows returned by a block cursor are called a 'row set'. The result set is fixed, the rowset is not. It changes position and contents each time a new set of rows is retrieved from the database. With block cursors, the method setRowSetSize() must be used with a parameter greater than 1. Navigation within the data represented by the SQLDBC_ResultSet object is possible using of navigation methods like first(), next(), previous(), relative() etc. When block cursors are used, after applying the navigation methods, the cursor points to the actual row set. For example assuming a result set size of 50 and a rowset size of 10, in the following sequence the block cursor points to the rows indicated:
In order to perform operations that operate on a single row only when multiple rows have been fetched, the application must indicate which row is the current row. When a block cursor first returns a row set, the current row is the first row of that row set. To change the current row, the application must call the member function setPos(). The data of a certain column in the current row can be retrieved by calling the method getObject(). Data fetched from the database is passed on to the application in variables that the application has allocated for this purpose. Before fetching the data from the database, the application bind these variables to the columns of the result set. Applications can bind any number of columns of the result set, including binding no columns at all. Binding of columns is done by calling to the member function bindColumn(). The column binding valid for all rows. After positioning the cursor through navigation methods, the data from the database is written into the bound column variables by a call to the member function fetch() of the row set of this result set. When block cursors are used, the number of rows actually filled can be determined with the member function getResultCount(). For unbounded columns, data can be written into application variables with getObject(), or - in case of block cursors - by calling setPos() on the rowset and then calling getObject(). |
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