Support MySQL SELECT INTO user variables and share INTO rendering

src/main/java/net/sf/jsqlparser/statement/StatementFeatureVisitor.java

@@ -65,6 +65,7 @@
 import net.sf.jsqlparser.statement.select.PivotVisitor;
 import net.sf.jsqlparser.statement.select.PivotVisitorAdapter;
 import net.sf.jsqlparser.statement.select.PlainSelect;
+import net.sf.jsqlparser.statement.select.MySqlSelectIntoClause;
 import net.sf.jsqlparser.statement.select.Select;
 import net.sf.jsqlparser.statement.select.SelectItem;
 import net.sf.jsqlparser.statement.select.SelectItemVisitor;
@@ -795,6 +796,12 @@ public <S> Void visit(PlainSelect plainSelect, S context) {
                 analysis.certain.remove(StmtFeature.RETURNS_RESULT_SET);
             }
 
+            MySqlSelectIntoClause mySqlInto = plainSelect.getMySqlSelectIntoClause();
+            if (mySqlInto != null && mySqlInto.getType() == MySqlSelectIntoClause.Type.VARIABLES) {
+                analysis.certain(StmtFeature.MODIFIES_SESSION);
+                analysis.certain.remove(StmtFeature.RETURNS_RESULT_SET);
+            }
+
             if (plainSelect.getForMode() != null) {
                 // FOR UPDATE / FOR SHARE take row locks
                 analysis.certain(StmtFeature.MODIFIES_TRANSACTION);

src/main/java/net/sf/jsqlparser/statement/select/MySqlSelectIntoClause.java

@@ -10,7 +10,11 @@
 package net.sf.jsqlparser.statement.select;
 
 import java.io.Serializable;
+import java.util.function.Consumer;
+import net.sf.jsqlparser.expression.Expression;
 import net.sf.jsqlparser.expression.StringValue;
+import net.sf.jsqlparser.expression.UserVariable;
+import net.sf.jsqlparser.expression.operators.relational.ExpressionList;
 import net.sf.jsqlparser.parser.ASTNodeAccessImpl;
 
 public class MySqlSelectIntoClause extends ASTNodeAccessImpl implements Serializable {
@@ -20,7 +24,7 @@ public enum Position {
     }
 
     public enum Type {
-        OUTFILE, DUMPFILE
+        OUTFILE, DUMPFILE, VARIABLES
     }
 
     public enum FieldsKeyword {
@@ -30,6 +34,7 @@ public enum FieldsKeyword {
     private Position position = Position.TRAILING;
     private Type type;
     private StringValue fileName;
+    private ExpressionList<UserVariable> variables;
     private String characterSet;
     private FieldsKeyword fieldsKeyword;
     private StringValue fieldsTerminatedBy;
@@ -60,6 +65,14 @@ public void setType(Type type) {
         this.type = type;
     }
 
+    public ExpressionList<UserVariable> getVariables() {
+        return variables;
+    }
+
+    public void setVariables(ExpressionList<UserVariable> variables) {
+        this.variables = variables;
+    }
+
     public StringValue getFileName() {
         return fileName;
     }
@@ -142,7 +155,19 @@ public boolean hasLinesClause() {
     }
 
     public StringBuilder appendTo(StringBuilder builder) {
-        builder.append("INTO ").append(type);
+        return appendTo(builder, expression -> builder.append(expression));
+    }
+
+    /** Shares INTO rendering while allowing deparsers to visit variable targets. */
+    public StringBuilder appendTo(StringBuilder builder, Consumer<Expression> expressionRenderer) {
+        builder.append("INTO ");
+        if (type == Type.VARIABLES) {
+            if (variables != null) {
+                expressionRenderer.accept(variables);
+            }
+            return builder;
+        }
+        builder.append(type);
         appendFileName(builder);
         appendCharacterSet(builder);
         appendFieldsClause(builder);

src/main/java/net/sf/jsqlparser/statement/select/SelectVisitorAdapter.java

@@ -164,6 +164,7 @@ public <S> T visit(PlainSelect plainSelect, S context) {
 
         if (plainSelect.getMySqlSelectIntoClause() != null) {
             MySqlSelectIntoClause mySqlSelectIntoClause = plainSelect.getMySqlSelectIntoClause();
+            expressionVisitor.visitExpressions(mySqlSelectIntoClause.getVariables(), context);
             expressionVisitor.visitExpression(mySqlSelectIntoClause.getFileName(), context);
             expressionVisitor.visitExpression(mySqlSelectIntoClause.getFieldsTerminatedBy(),
                     context);

src/main/java/net/sf/jsqlparser/util/deparser/SelectDeParser.java

@@ -258,11 +258,7 @@ public <S> StringBuilder visit(PlainSelect plainSelect, S context) {
             }
         }
 
-        if (plainSelect.getMySqlSelectIntoClause() != null
-                && plainSelect.getMySqlSelectIntoClause()
-                        .getPosition() == MySqlSelectIntoClause.Position.BEFORE_FROM) {
-            builder.append(" ").append(plainSelect.getMySqlSelectIntoClause());
-        }
+        deparseMySqlSelectInto(plainSelect, MySqlSelectIntoClause.Position.BEFORE_FROM, context);
 
         if (plainSelect.getFromItem() != null) {
             builder.append(" FROM ");
@@ -401,11 +397,7 @@ public <S> StringBuilder visit(PlainSelect plainSelect, S context) {
         if (plainSelect.isForUpdateBeforeOrderBy()) {
             deparseOrderByElementsClause(plainSelect, plainSelect.getOrderByElements());
         }
-        if (plainSelect.getMySqlSelectIntoClause() != null
-                && plainSelect.getMySqlSelectIntoClause()
-                        .getPosition() == MySqlSelectIntoClause.Position.TRAILING) {
-            builder.append(" ").append(plainSelect.getMySqlSelectIntoClause());
-        }
+        deparseMySqlSelectInto(plainSelect, MySqlSelectIntoClause.Position.TRAILING, context);
         if (plainSelect.getSettings() != null && !plainSelect.getSettings().isEmpty()) {
             builder.append(" SETTINGS ");
             deparseUpdateSets(plainSelect.getSettings(), builder, expressionVisitor);
@@ -720,6 +712,15 @@ public void setExpressionVisitor(ExpressionVisitor<StringBuilder> visitor) {
         expressionVisitor = visitor;
     }
 
+    private <S> void deparseMySqlSelectInto(PlainSelect select,
+            MySqlSelectIntoClause.Position position, S context) {
+        MySqlSelectIntoClause into = select.getMySqlSelectIntoClause();
+        if (into != null && into.getPosition() == position) {
+            builder.append(' ');
+            into.appendTo(builder, expression -> expression.accept(expressionVisitor, context));
+        }
+    }
+
     @SuppressWarnings({"PMD.CyclomaticComplexity"})
     public void deparseJoin(Join join) {
         if (join.isGlobal()) {

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -1420,6 +1420,20 @@ public class CCJSqlParser extends AbstractJSqlParser<CCJSqlParser> {
         return Dialect.MYSQL.name().equals(dialect) || Dialect.MARIADB.name().equals(dialect);
     }
 
+    private boolean isMySqlSelectIntoAhead() {
+        if (getToken(1).kind != K_INTO) { return false; }
+        int kind = getToken(2).kind;
+        return kind == K_OUTFILE || kind == K_DUMPFILE
+                || isMySqlDialect() && (kind == S_AT_IDENTIFIER || kind == K_AT_SIGN);
+    }
+
+    private static UserVariable requireMySqlIntoVariable(UserVariable variable) throws ParseException {
+        if (variable.isDoubleAdd()) {
+            throw new ParseException("INTO requires a user variable with a single @ prefix");
+        }
+        return variable;
+    }
+
     private ExplainStatement.OptionType postgresqlExplainOptionType(String name) throws ParseException {
         try {
             return ExplainStatement.OptionType.from(name);
@@ -6190,12 +6204,14 @@ PlainSelect PlainSelect() #PlainSelect:
 
     selectItems=SelectItemsList()
 
-    [ LOOKAHEAD(<K_INTO> (<K_OUTFILE> | <K_DUMPFILE>))
-        mySqlSelectIntoClause = MySqlSelectIntoClause(MySqlSelectIntoClause.Position.BEFORE_FROM)
-        { plainSelect.setMySqlSelectIntoClause(mySqlSelectIntoClause); }
-    ]
     [ LOOKAHEAD(<K_INTO>)
-        intoTables = IntoClause() { plainSelect.setIntoTables(intoTables); }
+        (
+            LOOKAHEAD({ isMySqlSelectIntoAhead() })
+            mySqlSelectIntoClause = MySqlSelectIntoClause(MySqlSelectIntoClause.Position.BEFORE_FROM)
+            { plainSelect.setMySqlSelectIntoClause(mySqlSelectIntoClause); }
+            |
+            intoTables = IntoClause() { plainSelect.setIntoTables(intoTables); }
+        )
     ]
     [ LOOKAHEAD(2) <K_FROM> fromItem=FromItem()
         [ LOOKAHEAD(2) lateralViews=LateralViews() ]
@@ -6287,7 +6303,12 @@ PlainSelect PlainSelect() #PlainSelect:
         ]
         [ LOOKAHEAD(2) interpolateElements = InterpolateClause() { plainSelect.setInterpolate(interpolateElements); } ]
     ]
-    [ LOOKAHEAD(<K_INTO> (<K_OUTFILE> | <K_DUMPFILE>))
+    [ LOOKAHEAD({ isMySqlSelectIntoAhead() })
+        {
+            if (mySqlSelectIntoClause != null || intoTables != null) {
+                throw new ParseException("Only one INTO clause is allowed per SELECT");
+            }
+        }
         mySqlSelectIntoClause = MySqlSelectIntoClause(MySqlSelectIntoClause.Position.TRAILING)
         { plainSelect.setMySqlSelectIntoClause(mySqlSelectIntoClause); }
     ]
@@ -6941,6 +6962,8 @@ MySqlSelectIntoClause MySqlSelectIntoClause(MySqlSelectIntoClause.Position posit
 {
     MySqlSelectIntoClause intoClause = new MySqlSelectIntoClause().withPosition(position);
     Token token;
+    ExpressionList<UserVariable> variables = new ExpressionList<UserVariable>();
+    UserVariable variable;
 }
 {
     <K_INTO>
@@ -6951,12 +6974,32 @@ MySqlSelectIntoClause MySqlSelectIntoClause(MySqlSelectIntoClause.Position posit
         |
           <K_DUMPFILE> { intoClause.setType(MySqlSelectIntoClause.Type.DUMPFILE); }
           token=<S_CHAR_LITERAL> { intoClause.setFileName(new StringValue(token.image)); }
+        |
+          LOOKAHEAD({ isMySqlDialect() })
+          variable=MySqlIntoVariable() { variables.add(variable); }
+          ( "," variable=MySqlIntoVariable() { variables.add(variable); } )*
+          { intoClause.setType(MySqlSelectIntoClause.Type.VARIABLES); intoClause.setVariables(variables); }
     )
     {
         return intoClause;
     }
 }
 
+UserVariable MySqlIntoVariable():
+{
+    UserVariable variable;
+    Token name;
+}
+{
+    (
+        variable=UserVariable()
+        |
+        <K_AT_SIGN> (name=<S_CHAR_LITERAL> | name=<S_QUOTED_IDENTIFIER>)
+        { variable = new UserVariable("@" + name.image); }
+    )
+    { return requireMySqlIntoVariable(variable); }
+}
+
 MySqlProcedureAnalyse MySqlProcedureAnalyse():
 {
     MySqlProcedureAnalyse procedureAnalyse = new MySqlProcedureAnalyse();

src/site/sphinx/usage.rst

@@ -716,6 +716,12 @@ One grammar covers every supported RDBMS, but a few pieces of syntax mean differ
 
 Features set explicitly *after* the preset win over it.
 
+MySQL user-variable targets in ``SELECT ... INTO @variable`` require
+``Dialect.MYSQL`` or ``Dialect.MARIADB``. They are stored in
+``PlainSelect.getMySqlSelectIntoClause().getVariables()`` as ``UserVariable``
+expressions, with the clause position preserved before ``FROM`` or at the end
+of the query. They are not table targets in ``getIntoTables()``.
+
 With ``Dialect.SQLSERVER``, ``PRIMARY KEY NONCLUSTERED (id)`` and
 ``UNIQUE CLUSTERED (id)`` store their clustering option in ``Index.getClustering()``
 for both ``CREATE TABLE`` and ``ALTER TABLE``. Without that dialect, these words