mysql 字段修改 public static void main(String[] args) { String filePath = "C:\\Users\\li-ningning\\Desktop\\fnTable.xls.xls";// filePath = "C:\\Users\\li-ningning\\Desktop\\master_data_fncrm.xls"; File file = new File(filePath); try { FileI
mysql 字段修改public static void main(String[] args) { String filePath = "C:\\Users\\li-ningning\\Desktop\\fnTable.xls.xls"; // filePath = "C:\\Users\\li-ningning\\Desktop\\master_data_fncrm.xls"; File file = new File(filePath); try { FileInputStream in = new FileInputStream(file); HSSFWorkbook wb = new HSSFWorkbook(in); // /获取第一张Sheet表 HSSFSheet st = wb.getSheetAt(0); for (int i = 0; i <= st.getLastRowNum(); i++) { String sql = "alter table "; HSSFRow row = st.getRow(i); if (row != null) { String tableName = toString((HSSFCell) row .getCell((short) 0)); String column = toString((HSSFCell) row.getCell((short) 1)); String length = toString((HSSFCell) row.getCell((short) 3)); int value = Integer.parseInt(length); sql += tableName; sql += " modify "; sql += column; if (value <= 50) { sql += " varchar(50)"; } else if (value <= 100) { sql += " varchar(100)"; } else if (value <= 150) { sql += " varchar(150)"; } else if (value <= 200) { sql += " varchar(200)"; } else if (value <= 250) { sql += " varchar(250)"; } else if (value <= 300) { sql += " varchar(300)"; } else if (value < 500) { sql += " varchar(500)"; } sql += ";"; String executeSql = sql; System.out.println(executeSql); sql = ""; } } } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } } public static String toString(HSSFCell cell) { String value = ""; if (cell == null) { return value; } cell.setEncoding(HSSFCell.ENCODING_UTF_16); switch (cell.getCellType()) { case HSSFCell.CELL_TYPE_STRING: value = cell.getStringCellValue().toString(); break; case HSSFCell.CELL_TYPE_NUMERIC: if (HSSFDateUtil.isCellDateFormatted(cell)) { Date date = cell.getDateCellValue(); if (date != null) { value = new SimpleDateFormat("yyyy-MM-dd").format(date); } else { value = ""; } } else { value = new DecimalFormat("0").format(cell .getNumericCellValue()); } break; case HSSFCell.CELL_TYPE_FORMULA: // 导入时如果为公式生成的数据则无值 if (!cell.getStringCellValue().equals("")) { value = cell.getStringCellValue(); } else { value = cell.getNumericCellValue() + ""; } break; case HSSFCell.CELL_TYPE_BLANK: break; case HSSFCell.CELL_TYPE_ERROR: value = ""; break; case HSSFCell.CELL_TYPE_BOOLEAN: value = (cell.getBooleanCellValue() ? "YES" : "NO"); break; default: value = ""; } return value.trim(); }
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mysqlviewshavelimitations:1)他們不使用Supportallsqloperations,限制DatamanipulationThroughViewSwithJoinsOrsubqueries.2)他們canimpactperformance,尤其是withcomplexcomplexclexeriesorlargedatasets.3)

porthusermanagementinmysqliscialforenhancingsEcurityAndsingsmenting效率databaseoperation.1)usecReateusertoAddusers,指定connectionsourcewith@'localhost'or@'%'。

mysqldoes notimposeahardlimitontriggers,butacticalfactorsdeterminetheireffactective:1)serverConfiguration impactactStriggerGermanagement; 2)複雜的TriggerSincreaseSySystemsystem load; 3)largertablesslowtriggerperfermance; 4)highConconcConcrencerCancancancancanceTigrignecentign; 5); 5)

Yes,it'ssafetostoreBLOBdatainMySQL,butconsiderthesefactors:1)StorageSpace:BLOBscanconsumesignificantspace,potentiallyincreasingcostsandslowingperformance.2)Performance:LargerrowsizesduetoBLOBsmayslowdownqueries.3)BackupandRecovery:Theseprocessescanbe

通過PHP網頁界面添加MySQL用戶可以使用MySQLi擴展。步驟如下:1.連接MySQL數據庫,使用MySQLi擴展。 2.創建用戶,使用CREATEUSER語句,並使用PASSWORD()函數加密密碼。 3.防止SQL注入,使用mysqli_real_escape_string()函數處理用戶輸入。 4.為新用戶分配權限,使用GRANT語句。

mysql'sblobissuitableForStoringBinaryDataWithInareLationalDatabase,而ilenosqloptionslikemongodb,redis和calablesolutionsolutionsolutionsoluntionsoluntionsolundortionsolunsonstructureddata.blobobobissimplobisslowdeperformberbutslowderformandperformancewithlararengedata;

toaddauserinmysql,使用:createUser'username'@'host'Indessify'password'; there'showtodoitsecurely:1)choosethehostcarecarefullytocon trolaccess.2)setResourcelimitswithoptionslikemax_queries_per_hour.3)usestrong,iniquepasswords.4)Enforcessl/tlsconnectionswith

toAvoidCommonMistakeswithStringDatatatPesInMysQl,CloseStringTypenuances,chosethirtightType,andManageEngencodingAndCollationsEttingSefectery.1)usecharforfixed lengengtrings,varchar forvariable-varchar forbariaible length,andtext/blobforlargerdataa.2 seterters seterters seterters


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