🐛 fix(table): 修复虚拟表全选丢失并完善导出/筛选能力

- 表头自定义组件保留 width，virtual 模式下选择列正常显示
  - 新增后端 ExportQuery，导出当前页/选中行避免长字段 IPC 截断
  - 筛选支持更多操作符并统一 WHERE 生成逻辑
  Close #57
  Close #56

frontend/src/utils/sql.ts

@@ -0,0 +1,173 @@
+export type FilterCondition = {
+  id?: number;
+  column?: string;
+  op?: string;
+  value?: string;
+  value2?: string;
+};
+
+const normalizeIdentPart = (ident: string) => {
+  let raw = (ident || '').trim();
+  if (!raw) return raw;
+  const first = raw[0];
+  const last = raw[raw.length - 1];
+  if ((first === '"' && last === '"') || (first === '`' && last === '`')) {
+    raw = raw.slice(1, -1).trim();
+  }
+  raw = raw.replace(/["`]/g, '').trim();
+  return raw;
+};
+
+export const quoteIdentPart = (dbType: string, ident: string) => {
+  const raw = normalizeIdentPart(ident);
+  if (!raw) return raw;
+  if ((dbType || '').toLowerCase() === 'mysql') return `\`${raw.replace(/`/g, '``')}\``;
+  return `"${raw.replace(/"/g, '""')}"`;
+};
+
+export const quoteQualifiedIdent = (dbType: string, ident: string) => {
+  const raw = (ident || '').trim();
+  if (!raw) return raw;
+  const parts = raw.split('.').map(normalizeIdentPart).filter(Boolean);
+  if (parts.length <= 1) return quoteIdentPart(dbType, raw);
+  return parts.map(p => quoteIdentPart(dbType, p)).join('.');
+};
+
+export const escapeLiteral = (val: string) => (val || '').replace(/'/g, "''");
+
+export const parseListValues = (val: string) => {
+  const raw = (val || '').trim();
+  if (!raw) return [];
+  return raw
+    .split(/[\n,，]+/)
+    .map(s => s.trim())
+    .filter(Boolean);
+};
+
+export const buildWhereSQL = (dbType: string, conditions: FilterCondition[]) => {
+  const whereParts: string[] = [];
+
+  (conditions || []).forEach((cond) => {
+    const op = (cond?.op || '').trim();
+    const column = (cond?.column || '').trim();
+    const value = (cond?.value ?? '').toString();
+    const value2 = (cond?.value2 ?? '').toString();
+
+    if (op === 'CUSTOM') {
+      const expr = value.trim();
+      if (expr) whereParts.push(`(${expr})`);
+      return;
+    }
+
+    if (!column) return;
+
+    const col = quoteIdentPart(dbType, column);
+
+    switch (op) {
+      case 'IS_NULL':
+        whereParts.push(`${col} IS NULL`);
+        return;
+      case 'IS_NOT_NULL':
+        whereParts.push(`${col} IS NOT NULL`);
+        return;
+      case 'IS_EMPTY':
+        // 兼容：空值通常理解为 NULL 或空字符串
+        whereParts.push(`(${col} IS NULL OR ${col} = '')`);
+        return;
+      case 'IS_NOT_EMPTY':
+        whereParts.push(`(${col} IS NOT NULL AND ${col} <> '')`);
+        return;
+      case 'BETWEEN': {
+        const v1 = value.trim();
+        const v2 = value2.trim();
+        if (!v1 || !v2) return;
+        whereParts.push(`${col} BETWEEN '${escapeLiteral(v1)}' AND '${escapeLiteral(v2)}'`);
+        return;
+      }
+      case 'NOT_BETWEEN': {
+        const v1 = value.trim();
+        const v2 = value2.trim();
+        if (!v1 || !v2) return;
+        whereParts.push(`${col} NOT BETWEEN '${escapeLiteral(v1)}' AND '${escapeLiteral(v2)}'`);
+        return;
+      }
+      case 'IN': {
+        const items = parseListValues(value);
+        if (items.length === 0) return;
+        const list = items.map(v => `'${escapeLiteral(v)}'`).join(', ');
+        whereParts.push(`${col} IN (${list})`);
+        return;
+      }
+      case 'NOT_IN': {
+        const items = parseListValues(value);
+        if (items.length === 0) return;
+        const list = items.map(v => `'${escapeLiteral(v)}'`).join(', ');
+        whereParts.push(`${col} NOT IN (${list})`);
+        return;
+      }
+      case 'CONTAINS': {
+        const v = value.trim();
+        if (!v) return;
+        whereParts.push(`${col} LIKE '%${escapeLiteral(v)}%'`);
+        return;
+      }
+      case 'NOT_CONTAINS': {
+        const v = value.trim();
+        if (!v) return;
+        whereParts.push(`${col} NOT LIKE '%${escapeLiteral(v)}%'`);
+        return;
+      }
+      case 'STARTS_WITH': {
+        const v = value.trim();
+        if (!v) return;
+        whereParts.push(`${col} LIKE '${escapeLiteral(v)}%'`);
+        return;
+      }
+      case 'NOT_STARTS_WITH': {
+        const v = value.trim();
+        if (!v) return;
+        whereParts.push(`${col} NOT LIKE '${escapeLiteral(v)}%'`);
+        return;
+      }
+      case 'ENDS_WITH': {
+        const v = value.trim();
+        if (!v) return;
+        whereParts.push(`${col} LIKE '%${escapeLiteral(v)}'`);
+        return;
+      }
+      case 'NOT_ENDS_WITH': {
+        const v = value.trim();
+        if (!v) return;
+        whereParts.push(`${col} NOT LIKE '%${escapeLiteral(v)}'`);
+        return;
+      }
+      case '=':
+      case '!=':
+      case '<':
+      case '<=':
+      case '>':
+      case '>=': {
+        const v = value.trim();
+        if (!v) return;
+        whereParts.push(`${col} ${op} '${escapeLiteral(v)}'`);
+        return;
+      }
+      default: {
+        // 兼容旧值：LIKE
+        if (op.toUpperCase() === 'LIKE') {
+          const v = value.trim();
+          if (!v) return;
+          whereParts.push(`${col} LIKE '%${escapeLiteral(v)}%'`);
+          return;
+        }
+
+        const v = value.trim();
+        if (!v) return;
+        whereParts.push(`${col} ${op} '${escapeLiteral(v)}'`);
+      }
+    }
+  });
+
+  return whereParts.length > 0 ? `WHERE ${whereParts.join(' AND ')}` : '';
+};
+