问题
How to set value for in clause in a preparedStatement in JDBC while executing a query.
Example:
connection.prepareStatement(\"Select * from test where field in (?)\");
If this in-clause can hold multiple values how can I do it. Sometimes I know the list of parameters beforehand or sometimes I don\'t know beforehand. How to handle this case?
回答1:
What I do is to add a "?" for each possible value.
For instance:
List possibleValues = ...
StringBuilder builder = new StringBuilder();
for( int i = 0 ; i < possibleValue.size(); i++ ) {
builder.append("?,");
}
String stmt = "select * from test where field in ("
+ builder.deleteCharAt( builder.length() -1 ).toString() + ")";
PreparedStatement pstmt = ...
And then happily set the params
int index = 1;
for( Object o : possibleValue ) {
pstmt.setObject( index++, o ); // or whatever it applies
}
回答2:
You could use setArray method as mentioned in the javadoc below:
http://docs.oracle.com/javase/6/docs/api/java/sql/PreparedStatement.html#setArray(int, java.sql.Array)
Code:
PreparedStatement statement = connection.prepareStatement("Select * from test where field in (?)");
Array array = statement.getConnection().createArrayOf("VARCHAR", new Object[]{"A1", "B2","C3"});
statement.setArray(1, array);
ResultSet rs = statement.executeQuery();
回答3:
You might want to check this link:
http://www.javaranch.com/journal/200510/Journal200510.jsp#a2
It explains the pros and cons of different methods of creating PreparedStatement with in clause.
EDIT:
An obvious approach is to dynamically generate the '?' part at runtime, but I don't want to merely suggest just this approach because depending on the way you use it, it might be inefficient (since the PreparedStatement will need to be 'compiled' every time it gets used)
回答4:
You can't replace ? in your query with an arbitrary number of values. Each ? is a placeholder for a single value only. To support an arbitrary number of values, you'll have to dynamically build a string containing ?, ?, ?, ... , ? with the number of question marks being the same as the number of values you want in your in clause.
回答5:
You need jdbc4 then you can use setArray!
In my case it didn't worked, as the UUID Datatype in postgres seems to still have its weak spots, but for the usual types it works.
ps.setArray(1, connection.createArrayOf("$VALUETYPE",myValuesAsArray));
Of course replace $VALUETYPE and myValuesAsArray with the correct values.
Remark following Marks comment:
Your database and the driver needs to support this! I tried Postgres 9.4 but I think this has been introduced earlier. You need a jdbc 4 driver, otherwise setArray won't be available. I used the postgresql 9.4-1201-jdbc41 driver that ships with spring boot
回答6:
What you can do is dynamically build the select string (the 'IN (?)' part) by a simple for loop as soon as you know how many values you need to put inside the IN clause. You can then instantiate the PreparedStatement.
回答7:
You don't want use PreparedStatment with dynamic queries using IN clause at least your sure you're always under 5 variable or a small value like that but even like that I think it's a bad idea ( not terrible, but bad ). As the number of elements is large, it will be worse ( and terrible ).
Imagine hundred or thousand possibilities in your IN clause :
It's counter-productive, you lost performance and memory because you cache every time a new request, and PreparedStatement are not just for SQL injection, it's about performance. In this case, Statement is better.
Your pool have a limit of PreparedStatment ( -1 defaut but you must limit it ), and you will reach this limit ! and if you have no limit or very large limit you have some risk of memory leak, and in extreme case OutofMemory errors. So if it's for your small personnal project used by 3 users it's not dramatic, but you don't want that if you're in a big company and that you're app is used by thousand people and million request.
Some reading. IBM : Memory utilization considerations when using prepared statement caching
回答8:
public static ResultSet getResult(Connection connection, List values) {
try {
String queryString = "Select * from table_name where column_name in";
StringBuilder parameterBuilder = new StringBuilder();
parameterBuilder.append(" (");
for (int i = 0; i < values.size(); i++) {
parameterBuilder.append("?");
if (values.size() > i + 1) {
parameterBuilder.append(",");
}
}
parameterBuilder.append(")");
PreparedStatement statement = connection.prepareStatement(queryString + parameterBuilder);
for (int i = 1; i < values.size() + 1; i++) {
statement.setInt(i, (int) values.get(i - 1));
}
return statement.executeQuery();
} catch (Exception d) {
return null;
}
}
回答9:
Currently, MySQL doesn't allow to set multiple values in one method call. So you have to have it under your own control. I usually create one prepared statement for predefined number of parameters, then I add as many batches as I need.
int paramSizeInClause = 10; // required to be greater than 0!
String color = "FF0000"; // red
String name = "Nathan";
Date now = new Date();
String[] ids = "15,21,45,48,77,145,158,321,325,326,327,328,329,330,331,332,333,334,335,336,337,338,339,340,341,342,343,344,345,346,347,348,349,350,351,358,1284,1587".split(",");
// Build sql query
StringBuilder sql = new StringBuilder();
sql.append("UPDATE book SET color=? update_by=?, update_date=? WHERE book_id in (");
// number of max params in IN clause can be modified
// to get most efficient combination of number of batches
// and number of parameters in each batch
for (int n = 0; n < paramSizeInClause; n++) {
sql.append("?,");
}
if (sql.length() > 0) {
sql.deleteCharAt(sql.lastIndexOf(","));
}
sql.append(")");
PreparedStatement pstm = null;
try {
pstm = connection.prepareStatement(sql.toString());
int totalIdsToProcess = ids.length;
int batchLoops = totalIdsToProcess / paramSizeInClause + (totalIdsToProcess % paramSizeInClause > 0 ? 1 : 0);
for (int l = 0; l < batchLoops; l++) {
int i = 1;
pstm.setString(i++, color);
pstm.setString(i++, name);
pstm.setTimestamp(i++, new Timestamp(now.getTime()));
for (int count = 0; count < paramSizeInClause; count++) {
int param = (l * paramSizeInClause + count);
if (param < totalIdsToProcess) {
pstm.setString(i++, ids[param]);
} else {
pstm.setNull(i++, Types.VARCHAR);
}
}
pstm.addBatch();
}
} catch (SQLException e) {
} finally {
//close statement(s)
}
If you don't like to set NULL when no more parameters left, you can modify code to build two queries and two prepared statements. First one is the same, but second statement for the remainder (modulus). In this particular example that would be one query for 10 params and one for 8 params. You will have to add 3 batches for the first query (first 30 params) then one batch for the second query (8 params).
回答10:
public class Test1 {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println("helow");
String where="where task in ";
where+="(";
// where+="'task1'";
int num[]={1,2,3,4};
for (int i=0;i<num.length+1;i++) {
if(i==1){
where +="'"+i+"'";
}
if(i>1 && i<num.length)
where+=", '"+i+"'";
if(i==num.length){
System.out.println("This is last number"+i);
where+=", '"+i+"')";
}
}
System.out.println(where);
}
}
回答11:
You can use :
for( int i = 0 ; i < listField.size(); i++ ) {
i < listField.size() - 1 ? request.append("?,") : request.append("?");
}
Then :
int i = 1;
for (String field : listField) {
statement.setString(i++, field);
}
Exemple :
List<String> listField = new ArrayList<String>();
listField.add("test1");
listField.add("test2");
listField.add("test3");
StringBuilder request = new StringBuilder("SELECT * FROM TABLE WHERE FIELD IN (");
for( int i = 0 ; i < listField.size(); i++ ) {
request = i < (listField.size() - 1) ? request.append("?,") : request.append("?");
}
DNAPreparedStatement statement = DNAPreparedStatement.newInstance(connection, request.toString);
int i = 1;
for (String field : listField) {
statement.setString(i++, field);
}
ResultSet rs = statement.executeQuery();
回答12:
try with this code
String ids[] = {"182","160","183"};
StringBuilder builder = new StringBuilder();
for( int i = 0 ; i < ids.length; i++ ) {
builder.append("?,");
}
String sql = "delete from emp where id in ("+builder.deleteCharAt( builder.length() -1 ).toString()+")";
PreparedStatement pstmt = connection.prepareStatement(sql);
for (int i = 1; i <= ids.length; i++) {
pstmt.setInt(i, Integer.parseInt(ids[i-1]));
}
int count = pstmt.executeUpdate();
回答13:
Many DBs have a concept of a temporary table, even assuming you don't have a temporary table you can always generate one with a unique name and drop it when you are done. While the overhead of creating and dropping a table is large, this may be reasonable for very large operations, or in cases where you are using the database as a local file or in memory (SQLite).
An example from something I am in the middle of (using Java/SqlLite):
String tmptable = "tmp" + UUID.randomUUID();
sql = "create table " + tmptable + "(pagelist text not null)";
cnn.createStatement().execute(sql);
cnn.setAutoCommit(false);
stmt = cnn.prepareStatement("insert into "+tmptable+" values(?);");
for(Object o : rmList){
Path path = (Path)o;
stmt.setString(1, path.toString());
stmt.execute();
}
cnn.commit();
cnn.setAutoCommit(true);
stmt = cnn.prepareStatement(sql);
stmt.execute("delete from filelist where path + page in (select * from "+tmptable+");");
stmt.execute("drop table "+tmptable+");");
Note that the fields used by my table are created dynamically.
This would be even more efficient if you are able to reuse the table.
回答14:
public static void main(String arg[]) {
Connection connection = ConnectionManager.getConnection();
PreparedStatement pstmt = null;
//if the field values are in ArrayList
List<String> fieldList = new ArrayList();
try {
StringBuffer sb = new StringBuffer();
sb.append(" SELECT * \n");
sb.append(" FROM TEST \n");
sb.append(" WHERE FIELD IN ( \n");
for(int i = 0; i < fieldList.size(); i++) {
if(i == 0) {
sb.append(" '"+fieldList.get(i)+"' \n");
} else {
sb.append(" ,'"+fieldList.get(i)+"' \n");
}
}
sb.append(" ) \n");
pstmt = connection.prepareStatement(sb.toString());
pstmt.executeQuery();
} catch (SQLException se) {
se.printStackTrace();
}
}
回答15:
Using Java 8 APIs,
List<Long> empNoList = Arrays.asList(1234, 7678, 2432, 9756556, 3354646);
List<String> parameters = new ArrayList<>();
empNoList.forEach(empNo -> parameters.add("?")); //Use forEach to add required no. of '?'
String commaSepParameters = String.join(",", parameters); //Use String to join '?' with ','
StringBuilder selectQuery = new StringBuilder().append("SELECT COUNT(EMP_ID) FROM EMPLOYEE WHERE EMP_ID IN (").append(commaSepParameters).append(")");
来源：https://stackoverflow.com/questions/3107044/preparedstatement-with-list-of-parameters-in-a-in-clause