import com.alibaba.druid.sql.dialect.mysql.ast.MySqlUnique; //导入依赖的package包/类
/**
 * only for show columns
 */
public boolean isUNI(String columnName) {
    for (SQLTableElement element : this.tableElementList) {
        if (element instanceof MySqlUnique) {
            MySqlUnique unique = (MySqlUnique) element;

            if (unique.getColumns().size() == 0) {
                continue;
            }

            SQLExpr column = unique.getColumns().get(0).getExpr();
            if (column instanceof SQLIdentifierExpr
                    && SQLUtils.nameEquals(columnName, ((SQLIdentifierExpr) column).getName())) {
                return unique.columns.size() == 1;
            } else if (column instanceof SQLMethodInvokeExpr
                    && SQLUtils.nameEquals(((SQLMethodInvokeExpr) column).getMethodName(), columnName)) {
                return true;
            }
        }
    }
    return false;
}
 

import com.alibaba.druid.sql.dialect.mysql.ast.MySqlUnique; //导入依赖的package包/类
public MySqlUnique findUnique(String columnName) {
    for (SQLTableElement element : this.tableElementList) {
        if (element instanceof MySqlUnique) {
            MySqlUnique unique = (MySqlUnique) element;

            if (unique.containsColumn(columnName)) {
                return unique;
            }
        }
    }

    return null;
}
 

import com.alibaba.druid.sql.dialect.mysql.ast.MySqlUnique; //导入依赖的package包/类
public MySqlUnique parseUnique() {
    accept(Token.UNIQUE);

    if (lexer.token() == Token.KEY) {
        lexer.nextToken();
    }

    if (lexer.token() == Token.INDEX) {
        lexer.nextToken();
    }

    MySqlUnique unique = new MySqlUnique();

    if (lexer.token() != Token.LPAREN) {
        SQLName indexName = name();
        unique.setIndexName(indexName);
    }

    accept(Token.LPAREN);
    for (; ; ) {
        unique.getColumns().add(this.expr());
        if (!(lexer.token() == (Token.COMMA))) {
            break;
        } else {
            lexer.nextToken();
        }
    }
    accept(Token.RPAREN);

    if (identifierEquals("USING")) {
        lexer.nextToken();
        unique.setIndexType(lexer.stringVal());
        lexer.nextToken();
    }

    return unique;
}
 

import com.alibaba.druid.sql.dialect.mysql.ast.MySqlUnique; //导入依赖的package包/类
public MySqlUnique parseUnique() {
    accept(Token.UNIQUE);

    if (lexer.token() == Token.KEY) {
        lexer.nextToken();
    }

    if (lexer.token() == Token.INDEX) {
        lexer.nextToken();
    }

    MySqlUnique unique = new MySqlUnique();

    if (lexer.token() != Token.LPAREN) {
        SQLName indexName = name();
        unique.setName(indexName);
    }
    
    //5.5语法 USING BTREE 放在index 名字后
    if (lexer.identifierEquals(FnvHash.Constants.USING)) {
        lexer.nextToken();
        unique.setIndexType(lexer.stringVal());
        lexer.nextToken();
    }

    accept(Token.LPAREN);
    for (;;) {
        SQLExpr column = this.expr();
        if (lexer.token() == Token.ASC) {
            column = new MySqlOrderingExpr(column, SQLOrderingSpecification.ASC);
            lexer.nextToken();
        } else if (lexer.token() == Token.DESC) {
            column = new MySqlOrderingExpr(column, SQLOrderingSpecification.DESC);
            lexer.nextToken();
        }
        unique.addColumn(column);
        if (!(lexer.token() == (Token.COMMA))) {
            break;
        } else {
            lexer.nextToken();
        }
    }
    accept(Token.RPAREN);

    if (lexer.identifierEquals(FnvHash.Constants.USING)) {
        lexer.nextToken();
        unique.setIndexType(lexer.stringVal());
        lexer.nextToken();
    }

    return unique;
}