{"id":13839,"date":"2021-08-13T14:57:23","date_gmt":"2021-08-13T14:57:23","guid":{"rendered":"https:\/\/freehost.page\/?p=13839"},"modified":"2021-08-13T14:57:23","modified_gmt":"2021-08-13T14:57:23","slug":"xu-ly-du-lieu-lon-hieu-qua","status":"publish","type":"post","link":"https:\/\/kiencang.net\/xu-ly-du-lieu-lon-hieu-qua\/","title":{"rendered":"X\u1eed l\u00fd d\u1eef li\u1ec7u l\u1edbn trong PHP v\u00e0 MySQL th\u1ebf n\u00e0o cho hi\u1ec7u qu\u1ea3?"},"content":{"rendered":"\n<p>S\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa 100 h\u00e0ng d\u1eef li\u1ec7u v\u00e0 100 ng\u00e0n hay th\u1eadm ch\u00ed l\u00e0 m\u1ed9t tri\u1ec7u h\u00e0ng d\u1eef li\u1ec7u l\u00e0 r\u1ea5t nhi\u1ec1u! \u1eea ai ch\u1ea3 bi\u1ebft!<\/p>\n\n\n\n<p>V\u1ea5n \u0111\u1ec1 \u1edf \u0111\u00e2y l\u00e0 v\u1edbi d\u1eef li\u1ec7u l\u1edbn b\u1ea1n kh\u00f4ng th\u1ec3 thao t\u00e1c th\u1ee7 c\u00f4ng \u0111\u01b0\u1ee3c. B\u1ea1n s\u1ebd ph\u1ea3i vi\u1ebft m\u00e3 \u0111\u1ec3 ch\u1ea1y t\u1ef1 \u0111\u1ed9ng. V\u00e0 n\u1ebfu m\u00e3 kh\u00f4ng hi\u1ec7u qu\u1ea3, thi\u1ebft b\u1ecb m\u00e0 b\u1ea1n ch\u1ea1y \u1ee9ng d\u1ee5ng c\u00f3 th\u1ec3 kh\u00f4ng kham n\u1ed5i.<\/p>\n\n\n\n<p>C\u00e1c kinh nghi\u1ec7m trong b\u00e0i vi\u1ebft n\u00e0y \u0111\u01b0\u1ee3c t\u00f4i r\u00fat ra khi ph\u00e2n t\u00edch m\u1ed9t b\u1ea3ng d\u1eef li\u1ec7u h\u1ecd t\u00ean c\u00f3 h\u01a1n 240 ng\u00e0n h\u00e0ng. B\u1ea3ng n\u00e0y bao g\u1ed3m 3 c\u1ed9t d\u1eef li\u1ec7u l\u00e0 h\u1ecd t\u00ean (<code>hoten<\/code>), ng\u00e0y th\u00e1ng n\u0103m sinh (<code>ngay<\/code>) v\u00e0 gi\u1edbi t\u00ednh (<code>gioi<\/code>).<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Chu\u1ea9n h\u00f3a d\u1eef li\u1ec7u<\/h2>\n\n\n\n<p>D\u1eef li\u1ec7u l\u1edbn th\u01b0\u1eddng thu nh\u1eadp t\u1eeb nhi\u1ec1u ngu\u1ed3n, ho\u1eb7c \u0111\u01b0\u1ee3c nh\u1eadp t\u1eeb nhi\u1ec1u ng\u01b0\u1eddi. \u0110i\u1ec1u \u0111\u00f3 d\u1eabn \u0111\u1ebfn t\u00ednh tr\u1ea1ng d\u1eef li\u1ec7u kh\u00f4ng \u0111\u01b0\u1ee3c \u0111\u1ed3ng b\u1ed9, v\u00ed d\u1ee5:<\/p>\n\n\n\n<ul><li>Ng\u00e0y th\u00e1ng n\u0103m \u0111\u01b0\u1ee3c vi\u1ebft b\u1edfi nhi\u1ec1u \u0111\u1ecbnh d\u1ea1ng nh\u01b0 dd\/mm\/yy, dd\/mm\/yyyy, mm\/dd\/yyyy, v\u00e2n v\u00e2n;<\/li><li>Ti\u1ebfng Vi\u1ec7t v\u1edbi c\u00e1c k\u00fd t\u1ef1 c\u00f3 d\u1ea5u nh\u01b0 \u1ec5, \u00f3, \u1eeb, v.v.. c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c m\u00e3 h\u00f3a th\u00e0nh 2 d\u1ea1ng kh\u00e1c nhau, d\u1eabn \u0111\u1ebfn vi\u1ec7c c\u00e2u l\u1ec7nh PHP \u0111\u1ec3 th\u1ed1ng k\u00ea sai s\u00f3t;<\/li><li>D\u1eef li\u1ec7u c\u00f3 sai s\u00f3t, ch\u1eb3ng h\u1ea1n nh\u01b0 d\u1eef li\u1ec7u gi\u1edbi t\u00ednh c\u1ee7a ng\u01b0\u1eddi b\u1ecb thi\u1ebfu, trong khi \u0111\u00e1ng ra ph\u1ea3i c\u00f3. H\u1ecd t\u00ean c\u00f3 c\u00e1c k\u00fd t\u1ef1 kh\u00f4ng ph\u1ea3i ch\u1eef c\u00e1i; <\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">C\u00e1c \u0111i\u1ec1u kh\u00f4ng n\u00ean l\u00e0m<\/h2>\n\n\n\n<ol><li><strong>L\u1eadp tr\u00ecnh tr\u1ef1c ti\u1ebfp tr\u00ean giao di\u1ec7n m\u00e1y ch\u1ee7 web hosting \u0111\u1ec3 thao t\u00e1c l\u1ec7nh<\/strong><\/li><\/ol>\n\n\n\n<p>\u0110i\u1ec1u n\u00e0y nghe c\u00f3 v\u1ebb ng\u1edb ng\u1ea9n, nh\u01b0ng t\u00f4i \u0111\u00e3 t\u1eebng vi\u1ebft l\u1ec7nh tr\u1ef1c ti\u1ebfp qua giao di\u1ec7n qu\u1ea3n tr\u1ecb c\u1ee7a control panel hosting! V\u00e0 ngay c\u1ea3 v\u1edbi VPS Vultr 4GB 2CPU, t\u1ed1c \u0111\u1ed9 th\u1ef1c thi l\u1ec7nh v\u1eabn k\u00e9m xa m\u00e1y t\u00ednh b\u00e0n \/ laptop c\u00f3 ch\u1ea5t l\u01b0\u1ee3ng t\u1ed1t. V\u00e0 t\u1ea5t nhi\u00ean th\u1ef1c hi\u1ec7n qua m\u00f4i tr\u01b0\u1eddng m\u00e1y t\u00ednh c\u00e1 nh\u00e2n b\u1ea1n c\u00f2n kh\u00f4ng t\u1ed1n ti\u1ec1n.<\/p>\n\n\n\n<p><a href=\"https:\/\/www.apachefriends.org\/index.html\" target=\"_blank\" rel=\"noreferrer noopener\">XAMPP<\/a> + <a href=\"https:\/\/netbeans.apache.org\/\" target=\"_blank\" rel=\"noreferrer noopener\">Apache Netbeans<\/a> + <a href=\"https:\/\/www.oracle.com\/java\/technologies\/javase\/javase-jdk8-downloads.html\" target=\"_blank\" rel=\"noreferrer noopener\">JDK SE<\/a> (c\u1ea7n khi b\u1ea1n c\u00e0i Netbeans) l\u00e0 \u0111\u1ee7 cho ch\u00fang ta, t\u1ea5t c\u1ea3 \u0111\u1ec1u mi\u1ec5n ph\u00ed, c\u00e0i \u0111\u1eb7t \u0111\u01a1n gi\u1ea3n. D\u0129 nhi\u00ean giao di\u1ec7n vi\u1ebft m\u00e3 c\u1ee7a Netbeans t\u1ed1t h\u01a1n nhi\u1ec1u giao di\u1ec7n c\u1ee7a control panel hosting.<\/p>\n\n\n\n<p>2. <strong>Vi\u1ebft m\u00e3 PHP x\u1eed l\u00fd d\u1eef li\u1ec7u qu\u00e1 c\u1ea9n th\u1eadn<\/strong><\/p>\n\n\n\n<p>Ch\u00fang ta c\u00f3 khuynh h\u01b0\u1edbng vi\u1ebft m\u00e3 x\u1eed l\u00fd t\u1ed5ng qu\u00e1t, bao tr\u00f9m nhi\u1ec1u tr\u01b0\u1eddng h\u1ee3p. \u0110\u00e2y l\u00e0 t\u01b0 duy nh\u00ecn chung l\u00e0 t\u1ed1t, v\u00ec n\u00f3 s\u1ebd gi\u00fap ch\u00fang ta ph\u00e1t tri\u1ec3n k\u1ef9 n\u0103ng v\u00e0 x\u1eed l\u00fd ch\u00ednh x\u00e1c trong nhi\u1ec1u b\u1ed1i c\u1ea3nh d\u1eef li\u1ec7u.<\/p>\n\n\n\n<p>Nh\u01b0ng c\u1ea7n s\u1eed d\u1ee5ng \u0111i\u1ec1u n\u00e0y m\u1ed9t c\u00e1ch h\u1ee3p l\u00fd, v\u00ec n\u00f3 s\u1ebd d\u1eabn \u0111\u1ebfn x\u1eed l\u00fd qu\u00e1 t\u1ea3i ho\u1eb7c r\u1ea5t ch\u1eadm.<\/p>\n\n\n\n<p>Ch\u1eb3ng h\u1ea1n \u0111\u1ec3 x\u1eed l\u00fd tr\u01b0\u1eddng d\u1eef li\u1ec7u gi\u1edbi t\u00ednh m\u00e0 ti\u00eau chu\u1ea9n ch\u1ec9 bao g\u1ed3m d\u1eef li\u1ec7u l\u00e0 nam v\u00e0 n\u1eef, t\u00f4i t\u1eebng ngh\u0129 c\u00e1ch x\u1eed l\u00fd nh\u01b0 sau:<\/p>\n\n\n\n<ul><li>Lo\u1ea1i b\u1ecf kho\u1ea3ng tr\u1eafng c\u00f3 trong d\u1eef li\u1ec7u b\u1eb1ng h\u00e0m <code>trim<\/code> v\u00e0 <code>preg_replace<\/code>;<\/li><li>Lo\u1ea1i b\u1ecf c\u00e1c k\u00fd t\u1ef1 kh\u00f4ng ph\u1ea3i v\u0103n b\u1ea3n b\u1eb1ng c\u00e1ch ch\u1ea1y m\u1ed9t m\u1ea3ng c\u00e1c k\u00fd t\u1ef1 kh\u00f4ng ph\u1ea3i v\u0103n b\u1ea3n k\u1ebft h\u1ee3p v\u1edbi h\u00e0m <code>str_replace<\/code>. \u0110\u00e2y l\u00e0 c\u00e2u l\u1ec7nh t\u1ed1n th\u1eddi gian v\u00ec m\u1ed9t d\u1eef li\u1ec7u qua \u0111\u00e2y s\u1ebd ph\u1ea3i ch\u1ea1y qua m\u1ea3ng g\u1ed3m g\u1ea7n 20 ph\u1ea7n t\u1eed;<\/li><li>Chuy\u1ec3n k\u00fd t\u1eeb v\u1ec1 d\u1ea1ng vi\u1ebft th\u01b0\u1eddng b\u1eb1ng h\u00e0m <code>mb_strtolower<\/code>;<\/li><\/ul>\n\n\n\n<p>\u0110i\u1ec1u d\u1edf \u1edf \u0111\u00e2y l\u00e0 m\u1eb7c d\u00f9 d\u1eef li\u1ec7u l\u1edbn, nh\u01b0ng v\u00ec c\u1ed9t gi\u1edbi t\u00ednh d\u1eef li\u1ec7u r\u1ea5t \u0111\u01a1n gi\u1ea3n, n\u00ean th\u1ef1c t\u1ebf v\u1ea5n \u0111\u1ec1 &#8220;c\u00f3 c\u00e1c k\u00fd t\u1ef1 kh\u00f4ng ph\u1ea3i v\u0103n b\u1ea3n&#8221; h\u00f3a ra KH\u00d4NG x\u1ea3y ra trong b\u1ea5t c\u1ee9 h\u00e0ng n\u00e0o trong h\u01a1n 240 ng\u00e0n h\u00e0ng d\u1eef li\u1ec7u m\u00e0 t\u00f4i c\u00f3.<\/p>\n\n\n\n<p>N\u00f3i c\u00e1ch kh\u00e1c vi\u1ec7c vi\u1ebft c\u00e2u l\u1ec7nh t\u1ed1n th\u1eddi gian th\u1ef1c thi nh\u1ea5t l\u00e0 ho\u00e0n to\u00e0n v\u00f4 \u00edch. V\u1eady n\u1ebfu d\u1eef li\u1ec7u kh\u00f4ng c\u1ea7n s\u1eeda th\u00ec ch\u00fang ta kh\u00f4ng n\u00ean vi\u1ebft m\u00e3 s\u1eeda l\u00e0m g\u00ec.<\/p>\n\n\n\n<p>\u0110\u1ec3 l\u00e0m \u0111\u01b0\u1ee3c \u0111i\u1ec1u \u0111\u00f3, ch\u00fang ta c\u1ea7n ph\u1ea3i x\u00e1c \u0111\u1ecbnh \u0111\u01b0\u1ee3c m\u1ee9c \u0111\u1ed9 sai l\u1ec7ch d\u1eef li\u1ec7u c\u1ee7a ch\u00fang ta \u0111ang \u1edf m\u1ee9c n\u00e0o, \u0111\u1ec3 c\u00e1c d\u00f2ng l\u1ec7nh kh\u00f4ng c\u1ea7n ph\u1ea3i th\u1ef1c thi nh\u1eefng nhi\u1ec7m v\u1ee5 kh\u00f4ng c\u1ea7n thi\u1ebft.<\/p>\n\n\n\n<p>M\u1ed9t trong nh\u1eefng c\u00e1ch \u0111\u01a1n gi\u1ea3n nh\u1ea5t \u0111\u1ec3 l\u00e0m \u0111i\u1ec1u n\u00e0y l\u00e0 s\u1eed d\u1ee5ng c\u00e2u l\u1ec7nh nh\u00f3m c\u00e1c ph\u1ea7n t\u1eed gi\u1ed1ng nhau \u0111\u1ec3 ph\u00e1t hi\u1ec7n c\u00e1c tr\u01b0\u1eddng d\u1eef li\u1ec7u b\u1ea5t th\u01b0\u1eddng, \u0111i\u1ec1u n\u00e0y \u0111\u1eb7c bi\u1ec7t ph\u00f9 h\u1ee3p v\u1edbi c\u00e1c c\u1ed9t d\u1eef li\u1ec7u c\u00f3 r\u1ea5t nhi\u1ec1u ph\u1ea7n t\u1eed nh\u01b0ng d\u1ea1ng c\u1ee5 th\u1ec3 c\u1ee7a ph\u1ea7n t\u1eed th\u00ec gi\u1edbi h\u1ea1n. Ch\u1eb3ng h\u1ea1n gi\u1edbi ch\u1ec9 c\u00f3  2 d\u1ea1ng c\u1ee5 th\u1ec3 l\u00e0 nam v\u00e0 n\u1eef. H\u1ecd ng\u01b0\u1eddi Vi\u1ec7t c\u0169ng ch\u1ec9 gi\u1edbi h\u1ea1n trong s\u1ed1 l\u01b0\u1ee3ng nh\u1ea5t \u0111\u1ecbnh (c\u1ee1 kho\u1ea3ng v\u00e0i tr\u0103m).<\/p>\n\n\n\n<p>C\u00e2u l\u1ec7nh SQL \u0111\u1ec3 b\u1ea1n nh\u00f3m c\u00e1c d\u1eef li\u1ec7u gi\u1ed1ng nhau l\u00e0:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT * , COUNT(*) AS number_record\nFROM ten_bang\nGROUP BY ten_cot_du_lieu_can_nhom\nHAVING number_record &gt; 0<\/code><\/pre>\n\n\n\n<p>K\u1ebft qu\u1ea3 c\u1ee7a t\u00f4i nh\u01b0 sau:<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"221\" height=\"89\" src=\"https:\/\/kiencang.net\/wp-content\/uploads\/2021\/08\/phat-hien-loi-du-lieu.png\" alt=\"th\u1ed1ng k\u00ea b\u1eb1ng SQL\" class=\"wp-image-13841\"\/><\/figure><\/div>\n\n\n\n<p>T\u1ee9c l\u00e0 th\u1ef1c t\u1ebf cho th\u1ea5y d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c nh\u1eadp v\u00e0o r\u1ea5t t\u1ed1t, ch\u1ec9 c\u00f3 8 h\u00e0ng nh\u1eadp sai v\u1edbi ch\u1ec9 k\u00fd t\u1ef1 N.<\/p>\n\n\n\n<p>C\u1ea9n th\u1eadn h\u01a1n b\u1ea1n c\u00f3 th\u1ec3 vi\u1ebft m\u00e3 \u0111\u01a1n gi\u1ea3n \u0111\u1ec3 th\u1ed1ng k\u00ea tr\u1ef1c ti\u1ebfp, v\u00ed d\u1ee5 trong tr\u01b0\u1eddng h\u1ee3p tr\u00ean t\u00f4i s\u1ebd d\u00f9ng c\u00e2u l\u1ec7nh PHP sau \u0111\u1ec3 bi\u1ebft \u0111\u01b0\u1ee3c m\u1ee9c \u0111\u1ed9 sai l\u1ec7ch d\u1eef li\u1ec7u \u1edf m\u1ee9c n\u00e0o:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>    session_start();\n    ob_start();\n    require 'database.php'; \/\/ tai database\n\n    $query3=\"SELECT gioi FROM hoten\";\n    $result3=$db-&gt;query($query3); \n    $nam=0;\n    $nu=0;\n    $sai=0;\n    $mangsai=array();\n    $hdl=0;\n    foreach ($result3 as $value3) {\n        if ($value3&#91;'gioi']==\"Nam\" || $value3&#91;'gioi']==\"nam\") {$nam++;} else {\n            if ($value3&#91;'gioi']==\"N\u1eef\" || $value3&#91;'gioi']==\"n\u1eef\") {$nu++;} else {$mangsai&#91;$sai]=$value3&#91;'gioi'];$sai++;}\n        }\n        $hdl++;\n    }\n    $tong = $nam + $nu + $sai; \n    echo \"Nam: \".$nam;\n    echo \"&lt;\/br&gt;\";\n    echo \"N\u1eef: \".$nu;\n    echo \"&lt;\/br&gt;\";\n    echo \"Sai d\u1eef li\u1ec7u: \".$sai;\n    echo \"&lt;\/br&gt;\";\n    echo \"T\u1ed5ng Nam + N\u1eef + Sai d\u1eef li\u1ec7u: \".$tong;\n    echo \"&lt;\/br&gt;\";\n    echo \"S\u1ed1 h\u00e0ng d\u1eef li\u1ec7u: \".$hdl;\n    echo \"&lt;\/br&gt;\";\n    echo \"C\u00e1c d\u1eef li\u1ec7u sai l\u1ec7ch:\";\n    echo \"&lt;\/br&gt;\";\n    for ($i=0;$i&lt;$sai;$i++) {\n        echo $mangsai&#91;$i].\"&lt;\/br&gt;\";\n    }<\/code><\/pre>\n\n\n\n<p>K\u1ebft qu\u1ea3:<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"331\" height=\"120\" src=\"https:\/\/kiencang.net\/wp-content\/uploads\/2021\/08\/dung-lenh-php.png\" alt=\"th\u1ed1ng k\u00ea b\u1eb1ng c\u00e2u l\u1ec7nh PHP\" class=\"wp-image-13843\" srcset=\"https:\/\/kiencang.net\/wp-content\/uploads\/2021\/08\/dung-lenh-php.png 331w, https:\/\/kiencang.net\/wp-content\/uploads\/2021\/08\/dung-lenh-php-300x109.png 300w\" sizes=\"(max-width: 331px) 100vw, 331px\" \/><\/figure><\/div>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"313\" height=\"164\" src=\"https:\/\/kiencang.net\/wp-content\/uploads\/2021\/08\/thong-ke-du-lieu-sai.png\" alt=\"\" class=\"wp-image-13844\" srcset=\"https:\/\/kiencang.net\/wp-content\/uploads\/2021\/08\/thong-ke-du-lieu-sai.png 313w, https:\/\/kiencang.net\/wp-content\/uploads\/2021\/08\/thong-ke-du-lieu-sai-300x157.png 300w\" sizes=\"(max-width: 313px) 100vw, 313px\" \/><\/figure><\/div>\n\n\n\n<p>\u0110i\u1ec1u \u0111\u00f3 cho th\u1ea5y t\u00f4i kh\u00f4ng c\u1ea7n ph\u1ea3i ph\u1ee9c t\u1ea1p h\u00f3a \u0111o\u1ea1n m\u00e3 x\u1eed l\u00fd c\u1ed9t gi\u1edbi t\u00ednh, ch\u1ec9 c\u1ea7n chuy\u1ec3n n\u00f3 v\u1ec1 d\u1ea1ng vi\u1ebft th\u01b0\u1eddng l\u00e0 \u0111\u1ee7.<\/p>\n\n\n\n<p>3. <strong>Kh\u00f4ng bi\u1ebft d\u00f9ng regular expression<\/strong><\/p>\n\n\n\n<p>\u1ede th\u1eddi \u0111i\u1ec3m hi\u1ec7n t\u1ea1i t\u00f4i c\u0169ng ch\u01b0a th\u00e0nh th\u1ea1o regular expression l\u1eafm, nh\u01b0ng khi m\u1edbi th\u1eed t\u00ecm hi\u1ec3u m\u1edbi th\u1ea5y s\u1ee9c m\u1ea1nh c\u1ee7a n\u00f3.<\/p>\n\n\n\n<p>Kh\u00f4ng bi\u1ebft regular expression b\u1ea1n c\u00f3 th\u1ec3 ph\u1ea3i vi\u1ebft v\u00e0i ch\u1ee5c d\u00f2ng m\u00e3 c\u1ed3ng k\u1ec1nh, c\u00f2n n\u1ebfu bi\u1ebft b\u1ea1n c\u00f3 c\u01a1 h\u1ed9i ch\u1ec9 ph\u1ea3i vi\u1ebft m\u1ed9t d\u00f2ng m\u00e0 th\u00f4i!<\/p>\n\n\n\n<p>V\u00ed d\u1ee5 \u0111\u00e2y l\u00e0 \u0111o\u1ea1n m\u00e3 c\u1ed3ng k\u1ec1nh t\u00f4i d\u00f9ng \u0111\u1ec3 ph\u00e1t hi\u1ec7n m\u1ed9t d\u1eef li\u1ec7u ng\u00e0y th\u00e1ng n\u0103m kh\u00f4ng ph\u1ea3i l\u00e0 d\u1ea1ng dd\/mm\/yyyy<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>preg_match('\/&#91;a-z]\/', '$ngaythangnam', $matches1); \/\/ d\u00f9ng \u0111\u1ec3 ki\u1ec3m tra c\u00f3 k\u00fd t\u1ef1 abc,..xyz trong d\u1eef li\u1ec7u ng\u00e0y th\u00e1ng n\u0103m hay kh\u00f4ng\n\nif (count($matches1) &gt; 0) {echo \"c\u00f3 l\u1ed7i 1\";}\n\necho \"&lt;\/br&gt;\";\n\n$kytuloi = array('?',')', '(', '&#91;', ']', '{', '}', '.', ',', '\"', ':', ';', '~', '!', '@', '#', '%', '^', '&amp;', '*', '+', '=', '-', '_', '&gt;', '&lt;'); \/\/\n$t = count($kytuloi);\n$loi=array();\n for ($i=0;$i&lt;$t;$i++) {\n     $l=mb_strpos($ngaythangnam,$kytuloi&#91;$i]);\n     if ($l&gt;0) {$loi&#91;$i]=1;}\n }\nif (count($loi) &gt; 0) {echo 'c\u00f3 l\u1ed7i 2';} \/\/d\u00f9ng \u0111\u1ec3 ki\u1ec3m tra c\u00f3 c\u00e1c k\u00fd t\u1ef1 \u0111\u1eb7c bi\u1ec7t trong d\u1eef li\u1ec7u ng\u00e0y th\u00e1ng hay kh\u00f4ng\n\n$gach=substr_count('$ngaythangnam', '\/');\nif ($gach!=2) {echo 'c\u00f3 l\u1ed7i 3';} \/\/d\u00f9ng \u0111\u1ec3 ki\u1ec3m tra d\u1eef li\u1ec7u c\u00f3 ph\u1ea3i l\u00e0 d\u1ea1ng ph\u00e2n c\u00e1ch nhau b\u1eb1ng d\u1ea5u \/ v\u00e0 c\u00f3 \u0111\u1ee7 2 d\u1ea5u hay kh\u00f4ng<\/code><\/pre>\n\n\n\n<p>Trong khi \u0111\u00f3 ch\u1ec9 v\u1edbi m\u1ed9t d\u00f2ng l\u1ec7nh sau, t\u00f4i s\u1ebd bi\u1ebft \u0111\u01b0\u1ee3c d\u1eef li\u1ec7u c\u00f3 h\u1ee3p chu\u1ea9n hay kh\u00f4ng:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>preg_match('\/\\b\\d{1,2}\\\/\\d{1,2}\\\/\\d{4}\\b\/', $ngaythangnam, $matches);<\/code><\/pre>\n\n\n\n<p>C\u1ee5m <code> \\b\\d{1,2}\\\/\\d{1,2}\\\/\\d{4}\\b<\/code> ch\u00ednh l\u00e0 c\u00e1i gi\u00fap ch\u00fang ta kh\u00f4ng ph\u1ea3i vi\u1ebft qu\u00e1 nhi\u1ec1u m\u00e3. N\u00f3 n\u00f3i r\u1eb1ng d\u1eef li\u1ec7u c\u1ea7n ph\u1ea3i ph\u00e2n c\u00e1ch b\u1eb1ng d\u1ea5u \/ v\u1edbi d\u1ea1ng nh\u01b0 sau 1 ho\u1eb7c 2 k\u00fd t\u1ef1 s\u1ed1 \/ 1 ho\u1eb7c 2 k\u00fd t\u1ef1 s\u1ed1 \/ ph\u1ea3i c\u00f3 4 k\u00fd t\u1ef1 s\u1ed1. \u0110\u00e2y ch\u00ednh l\u00e0 \u0111\u1ecbnh d\u1ea1ng dd\/mm\/yyyyy c\u1ee7a ch\u00fang ta.<\/p>\n\n\n\n<p>4. <strong>Kh\u00f4ng s\u1eed d\u1ee5ng t\u00ednh n\u0103ng Search \/ T\u00ecm ki\u1ebfm trong SQL<\/strong><\/p>\n\n\n\n<p>T\u00ednh n\u0103ng n\u00e0y gi\u00fap ch\u00fang ta ki\u1ec3m tra r\u1ea5t nhanh c\u00e1c d\u1eef li\u1ec7u l\u1ec7ch chu\u1ea9n thay v\u00ec ph\u1ea3i ng\u1ed3i vi\u1ebft l\u1ec7nh PHP.<\/p>\n\n\n\n<p>M\u1ed9t s\u1ed1 to\u00e1n t\u1eed quan tr\u1ecdng bao g\u1ed3m:<\/p>\n\n\n\n<ul><li>To\u00e1n t\u1eed = \u0111\u1ec3 so kh\u1edbp ch\u00ednh x\u00e1c;<\/li><li>To\u00e1n t\u1eed is NULL \u0111\u1ec3 ph\u00e1t hi\u1ec7n d\u1eef li\u1ec7u NULL \/ Kh\u00f4ng c\u00f3 d\u1eef li\u1ec7u;<\/li><li>Bi\u1ec3u th\u1ee9c ch\u00ednh quy REGEXP, \u0111\u00f3 ch\u00ednh l\u00e0 regular expression;<\/li><\/ul>\n\n\n\n<p>Th\u1ef1c t\u1ebf h\u00ecnh th\u1ee9c t\u00ecm ki\u1ebfm n\u00e0o b\u1ea1n d\u00f9ng c\u00f2n ph\u1ee5 thu\u1ed9c v\u00e0o ki\u1ec3u d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n. \u1ede tr\u00ean ch\u1ec9 l\u00e0 kinh nghi\u1ec7m ri\u00eang v\u1edbi d\u1eef li\u1ec7u h\u1ecd t\u00ean m\u00e0 t\u00f4i c\u1ea7n thao t\u00e1c.<\/p>\n\n\n\n<p>V\u00ed d\u1ee5 v\u1edbi d\u1eef li\u1ec7u ng\u00e0y th\u00e1ng n\u0103m sinh, t\u00f4i th\u1eed d\u00f9ng  \\b\\d{1,2}\\\/\\d{1,2}\\\/\\d{4}\\b  trong SQL th\u00ec k\u1ebft qu\u1ea3 cho th\u1ea5y t\u1ea5t c\u1ea3 d\u1eef li\u1ec7u kh\u00e1c NULL \u0111\u1ec1u h\u1ee3p chu\u1ea9n.<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"687\" height=\"369\" src=\"https:\/\/kiencang.net\/wp-content\/uploads\/2021\/08\/kiem-tra-data-sql.png\" alt=\"ki\u1ec3m tra d\u1eef li\u1ec7u b\u1eb1ng t\u00ednh n\u0103ng t\u00ecm ki\u1ebfm trong SQL\" class=\"wp-image-13848\" srcset=\"https:\/\/kiencang.net\/wp-content\/uploads\/2021\/08\/kiem-tra-data-sql.png 687w, https:\/\/kiencang.net\/wp-content\/uploads\/2021\/08\/kiem-tra-data-sql-300x161.png 300w\" sizes=\"(max-width: 687px) 100vw, 687px\" \/><\/figure><\/div>\n\n\n\n<p>\u0110i\u1ec1u n\u00e0y m\u1ed9t l\u1ea7n n\u1eefa gi\u00fap t\u00f4i bi\u1ebft \u0111\u01b0\u1ee3c r\u1eb1ng m\u00ecnh kh\u00f4ng c\u1ea7n ph\u1ea3i vi\u1ebft h\u00e0m x\u1eed l\u00fd ng\u00e0y th\u00e1ng ph\u1ee9c t\u1ea1p.<\/p>\n\n\n\n<p>5. <strong>S\u1eed d\u1ee5ng b\u1ed9 m\u00e3 utf8_general_ci<\/strong><\/p>\n\n\n\n<p><code>utf8_general_ci<\/code> l\u00e0 b\u1ed9 m\u00e3 kh\u00f4ng hi\u1ec7u qu\u1ea3 \u0111\u1ec3 s\u1eafp x\u1ebfp, ph\u00e2n t\u00edch d\u1eef li\u1ec7u trong SQL. V\u1edbi ki\u1ec3u m\u00e3 h\u00f3a kh\u00e1c nhau c\u1ee7a ti\u1ebfng Vi\u1ec7t, <code>utf8_general_ci<\/code> s\u1ebd \u0111\u01b0a ra c\u00e1c k\u1ebft qu\u1ea3 kh\u00f4ng nh\u01b0 \u00fd.<\/p>\n\n\n\n<p>B\u1ed9 m\u00e3 t\u1ed1t h\u01a1n m\u00e0 b\u1ea1n n\u00ean d\u00f9ng l\u00e0 <strong><code>utf8mb4_unicode_ci<\/code><\/strong><\/p>\n\n\n\n<p>6. <strong>\u0110\u1ec3 th\u1eddi gian th\u1ef1c hi\u1ec7n l\u1ec7nh PHP theo m\u1eb7c \u0111\u1ecbnh<\/strong><\/p>\n\n\n\n<p>M\u1eb7c \u0111\u1ecbnh c\u00f3 th\u1ec3 l\u00e0 120 gi\u00e2y, tuy nhi\u00ean tr\u00ean c\u00e1c \u1ee9ng d\u1ee5ng x\u1eed l\u00fd d\u1eef li\u1ec7u l\u1edbn, th\u1eddi gian n\u00e0y kh\u00f4ng \u0111\u1ee7. V\u1edbi l\u01b0\u1ee3ng data g\u1ed3m 240 ng\u00e0n d\u1eef li\u1ec7u, t\u00f4i c\u00f3 th\u1ec3 c\u1ea7n \u0111\u1ebfn 5 ph\u00fat \u0111\u1ec3 ch\u1ea1y l\u1ec7nh.<\/p>\n\n\n\n<p>C\u00e1ch \u0111\u1ec3 b\u1ea1n n\u00e2ng con s\u1ed1 n\u00e0y l\u00ean l\u00e0 th\u00eam d\u00f2ng sau v\u00e0o file .php m\u00e0 b\u1ea1n c\u1ea7n th\u1ef1c thi:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>set_time_limit(600); \/\/ t\u01b0\u01a1ng \u0111\u01b0\u01a1ng v\u1edbi 10 ph\u00fat = 600 gi\u00e2y<\/code><\/pre>\n\n\n\n<p>7. <strong>Chia d\u1eef li\u1ec7u ra \u0111\u1ec3 x\u1eed l\u00fd<\/strong><\/p>\n\n\n\n<p>Trong tr\u01b0\u1eddng h\u1ee3p \u00e1p d\u1ee5ng m\u1ecdi c\u00e1ch m\u00e0 vi\u1ec7c x\u1eed l\u00fd d\u1eef li\u1ec7u v\u1eabn qu\u00e1 t\u1ea3i th\u00ec b\u1ea1n n\u00ean chia nh\u1ecf d\u1eef li\u1ec7u ra.<\/p>\n\n\n\n<p>Vi\u1ec7c chia nh\u1ecf c\u00f3 th\u1ec3 d\u00f9ng m\u1ed9t trong 2 c\u00e1ch sau:<\/p>\n\n\n\n<ul><li>B\u1ea1n chia l\u00e0m nhi\u1ec1u b\u1ea3ng d\u1eef li\u1ec7u;<\/li><li>B\u1ea1n s\u1eed d\u1ee5ng c\u00e2u l\u1ec7nh \u0111i\u1ec1u ki\u1ec7n WHERE trong SQL \u0111\u1ec3 SELECT gi\u1edbi h\u1ea1n m\u1ed9t s\u1ed1 l\u01b0\u1ee3ng b\u1ea3n ghi nh\u1ea5t \u0111\u1ecbnh, thay v\u00ec ch\u1ecdn to\u00e0n b\u1ed9 b\u1ea3n ghi trong b\u1ea3ng;<\/li><\/ul>\n","protected":false},"excerpt":{"rendered":"<p>S\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa 100 h\u00e0ng d\u1eef li\u1ec7u v\u00e0 100 ng\u00e0n hay th\u1eadm ch\u00ed l\u00e0 m\u1ed9t tri\u1ec7u h\u00e0ng d\u1eef li\u1ec7u l\u00e0 r\u1ea5t nhi\u1ec1u! \u1eea ai ch\u1ea3 bi\u1ebft! V\u1ea5n \u0111\u1ec1 \u1edf \u0111\u00e2y l\u00e0 v\u1edbi d\u1eef li\u1ec7u l\u1edbn b\u1ea1n kh\u00f4ng th\u1ec3 thao t\u00e1c th\u1ee7 c\u00f4ng \u0111\u01b0\u1ee3c. B\u1ea1n s\u1ebd ph\u1ea3i vi\u1ebft m\u00e3 \u0111\u1ec3 ch\u1ea1y t\u1ef1 \u0111\u1ed9ng. 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