[英]SQL query in Java Code does not work properly
我在JAVA中使用SQL查詢遇到問題。
JAVA代碼:
public boolean zeKontrolaExistujiciZalohyTest(String datum) {
try {
connected();
boolean existujeZaloha = false;
int pocet;
ResultSet rs = statement.executeQuery("SELECT count(id) FROM "+table_ze+"\n" +
"WHERE TO_CHAR(TO_DATE(datum, 'dd.mm.yyyy'), 'mm.yyyy') = TO_CHAR(TO_DATE('"+datum+"', 'dd.mm.yyyy'), 'mm.yyyy')");
rs.next();
pocet = rs.getInt(1);
rs.close();
closed();
if (pocet >= 0) {
existujeZaloha = true;
} else {
existujeZaloha = false;
}
return existujeZaloha;
} catch (Exception e) {
e.printStackTrace();
Dialogs.create()
.title("Exception Dialog")
.showException(e);
return true;
}
}
SQL Developer中的SQL查詢:
SELECT count(id) FROM pbtest.u_zalohy_energie
WHERE TO_CHAR(TO_DATE(datum, 'dd.mm.yyyy'), 'mm.yyyy') = TO_CHAR(TO_DATE('15.09.2014', 'dd.mm.yyyy'), 'mm.yyyy');
當我運行JAVA代碼時,結果變量為“ pocet = 0”。 但是,當我在任何SQL Developer中運行SQL查詢時,結果列COUNT(id)為“ 1”。
當我更改SQL查詢時,讓我運行JAVA代碼重新調整變量“ pocet = 1”。
更改SQL代碼:
ResultSet rs = statement.executeQuery("SELECT count(id) FROM "+table_ze+"\n" +
"WHERE datum = TO_DATE('"+datum+"', 'dd.mm.yyyy')");
有人知道問題出在哪里嗎?
有關信息:我使用一個Oracle數據庫。
謝謝。
datum
是字符串
SELECT count(id)
FROM pbtest.u_zalohy_energie
WHERE TO_DATE(datum, 'dd.mm.yyyy') = TO_DATE('15.09.2014', 'dd.mm.yyyy');
datum
是日期
SELECT count(id)
FROM pbtest.u_zalohy_energie
WHERE TRUNC(datum) = TO_DATE('15.09.2014', 'dd.mm.yyyy');
如果數據是日期,則它也可能包含時間成分。 因此將其刪除。 使用TRUNC()
TRUNC(datum) = TO_DATE('15.09.2014', 'dd.mm.yyyy');
Java代碼:
ResultSet rs = statement.executeQuery("SELECT count(id) FROM "+table_ze+"\n" +
"WHERE TRUNC(datum) = TO_DATE('"+datum+"', 'dd.mm.yyyy')");
您的陳述式語法錯誤
ResultSet rs = statement.executeQuery("SELECT count(id) FROM "+table_ze+"\n" +
"WHERE TO_CHAR(TO_DATE(datum, 'dd.mm.yyyy'), 'mm.yyyy') = TO_CHAR(TO_DATE('"+datum+"', 'dd.mm.yyyy'), 'mm.yyyy')");
執行的查詢將是
SELECT count(id) FROM pbtest.u_zalohy_energie\nWHERE TO_CHAR(TO_DATE(datum, 'dd.mm.yyyy'), 'mm.yyyy') = TO_CHAR(TO_DATE('15.09.2014'', 'dd.mm.yyyy'), 'mm.yyyy')")
您應該刪除“ \\ n”,因為這不會導致換行。
嘗試一下
ResultSet rs = statement.executeQuery("SELECT count(id) FROM " + table_ze
+ " WHERE TO_CHAR(TO_DATE(datum, 'dd.mm.yyyy'), 'mm.yyyy') = TO_CHAR(TO_DATE('"+datum+"', 'dd.mm.yyyy'), 'mm.yyyy')");
還應考慮Maheswaran Ravisankar關於以下內容的評論:“ ... PreparedStatement和綁定變量以避免SQL * Injection”
謝謝您的建議,我解決了如下問題:
public boolean zeKontrolaExistujiciZalohy(String datum, String typZalohy, String zalohaNaMesic) {
connected();
boolean existujeZaloha = false;
int pocet = 0;
ResultSet rs;
PreparedStatement pstmt = null;
try{
statement = connection.createStatement();
String SQL = "SELECT count(id) AS pocet FROM " + table_ze + " WHERE (EXTRACT(MONTH FROM datum)) = (EXTRACT(MONTH FROM to_date(?, 'dd.mm.yyyy'))) "
+ "AND (EXTRACT(YEAR FROM datum)) = (EXTRACT(YEAR FROM to_date(?, 'dd.mm.yyyy')))"
+ "AND typ_zalohy = ? "
+ "AND zaloha_na_mesic = ? ";
pstmt = connection.prepareStatement(SQL);
pstmt.setString(1, datum);
pstmt.setString(2, datum);
pstmt.setString(3, typZalohy);
pstmt.setString(4, zalohaNaMesic);
rs = pstmt.executeQuery();
while(rs.next()){
pocet = rs.getInt("pocet");
}
rs.close();
if (pocet > 0) {
existujeZaloha = true;
} else {
existujeZaloha = false;
}
return existujeZaloha;
}
catch(SQLException ex){
Dialogs.create()
.title("Exception Dialog")
.showException(ex);
return true;
}
}
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