{"id":134,"date":"2013-05-24T00:17:41","date_gmt":"2013-05-23T16:17:41","guid":{"rendered":"http:\/\/www.gpfeng.com\/?p=134"},"modified":"2014-03-13T21:22:02","modified_gmt":"2014-03-13T13:22:02","slug":"oraclepostgresql-update-returning-%e5%9c%a8mysql%e4%b8%ad%e7%9a%84%e5%ae%9e%e7%8e%b0","status":"publish","type":"post","link":"http:\/\/www.gpfeng.com\/?p=134","title":{"rendered":"Oracle\/PostgreSQL UPDATE&#8230;RETURNING&#8230;\u5728MySQL\u4e2d\u7684\u5b9e\u73b0"},"content":{"rendered":"<h3>\u9700\u6c42\u63cf\u8ff0<\/h3>\n<p>\u6700\u8fd1\u5f00\u53d1\u63d0\u4e86\u8fd9\u6837\u4e00\u4e2a\u9700\u6c42\uff1a<\/p>\n<pre lang=\"mysql\">BEGIN;\r\nUPDATE products SET quantity=quantity-1 WHERE product_id=123456;\r\nSELECT quantity FROM products WHERE product_id=123456;\r\nCOMMIT;<\/pre>\n<p>\u5728\u4e00\u4e2a\u4e8b\u52a1\u4e2dUPDATE\u4e4b\u540e\u9700\u8981SELECT\u51fa\u66f4\u65b0\u540e\u7684\u503c\uff0c\u5e0c\u671b\u5728MySQL\u4e2d\u80fd\u53ea\u4f7f\u7528\u4e00\u6761SQL\u5c31\u80fd\u505a\u5230\uff0c\u8fd9\u6837\u65e2\u53ef\u4ee5\u65b9\u4fbf\u5f00\u53d1\uff0c\u53c8\u53ef\u4ee5\u5927\u5927\u51cf\u5c0f\u4e8b\u52a1\u5904\u7406\u65f6\u95f4\uff0c\u5176\u5b9e\u8fd9\u4e2a\u9700\u6c42\u5728Oracle\/PostgreSQL\u4e2d\u5df2\u7ecf\u6709\u76f8\u5e94\u7684\u8bed\u6cd5\u652f\u6301\uff0c<a href=\"http:\/\/www.postgresql.org\/docs\/9.1\/static\/sql-update.html\">PostgreSQL UPDATE<\/a>\uff0c\u5b9e\u73b0\u8fd9\u4e2a\u9700\u6c42\u8fd8\u6709\u4e00\u4e2a\u524d\u63d0\uff1a\u4e0d\u4fee\u6539MySQL\u670d\u52a1\u5668\/\u5ba2\u6237\u7aef\u534f\u8bae\uff0c\u80fd\u591f\u517c\u5bb9JDBC<br \/>\n<!--more--><br \/>\n\u6700\u521d\u7684\u60f3\u6cd5\u662f\u76f4\u63a5\u91c7\u7528UPDATE&#8230;RETURNING\u8bed\u6cd5\uff0c\u4e0a\u8ff0\u4e8b\u52a1\u4e2d\u7684\u4e24\u6761SQL\u53ea\u9700\u8981\u4e00\u6761\u5c31\u80fd\u5b9e\u73b0\u529f\u80fd\uff1a<\/p>\n<pre lang=\"mysql\">UPDATE products SET quantity=quantity-1 WHERE product_id=123456 RETURNING quantity;<\/pre>\n<p>\u7136\u800cmysql-connector\u5e76\u6ca1\u6709\u7ed9\u6211\u4eec\u7559\u4e0b\u53d1\u6325\u7a7a\u95f4\uff1a<br \/>\njava\u4e2dStatement\u6267\u884csql\u4e3b\u8981\u6709\u4e24\u4e2a\u65b9\u6cd5\uff1aStatement.executeQuery\u548cStatement.executeUpdate,\u524d\u8005\u7684\u8fd4\u56de\u7ed3\u679c\u662fResultSet\uff0c\u4e3b\u8981\u7528\u4e8e\u6267\u884cSELECT\uff0c\u540e\u8005\u53ea\u8fd4\u56deint,\u4e3b\u8981\u7528\u4e8e\u6267\u884cDDL\/DML,\u6211\u4eec\u9700\u8981\u8fd4\u56deResultSet\uff0c\u90a3\u4e48\u53ea\u80fd\u8c03\u7528executeQuery\u63a5\u53e3\uff0c\u7136\u800c\u7528\u4e00\u6761UPDATE\u8bed\u53e5\u6267\u884c\u65f6\u4f1a\u62a5\u9519\uff0c\u539f\u56e0\u662fmysql-connector\u4e2d\u7684StatementImpl\u7c7b\u5728\u5b9e\u73b0executeQuery\u65b9\u6cd5\u65f6\u5bf9\u4f20\u5165sql\u505a\u68c0\u67e5\uff0c\u5177\u4f53\u51fd\u6570\uff1acheckForDml<\/p>\n<pre lang=\"mysql\">protected void checkForDml(String sql, char firstStatementChar)\r\n\t\tthrows SQLException {\r\n  if ((firstStatementChar == 'I') || (firstStatementChar == 'U')\r\n      || (firstStatementChar == 'D') || (firstStatementChar == 'A')\r\n      || (firstStatementChar == 'C') || (firstStatementChar == 'T')\r\n      || (firstStatementChar == 'R')) {\r\n\r\n    String noCommentSql = StringUtils.stripComments(sql, \"'\\\"\", \"'\\\"\", true, false, true, true);\r\n\r\n    if (StringUtils.startsWithIgnoreCaseAndWs(noCommentSql, \"INSERT\") \/\/$NON-NLS-1$\r\n        || StringUtils.startsWithIgnoreCaseAndWs(noCommentSql, \"UPDATE\") \/\/$NON-NLS-1$\r\n        || StringUtils.startsWithIgnoreCaseAndWs(noCommentSql, \"DELETE\") \/\/$NON-NLS-1$\r\n        || StringUtils.startsWithIgnoreCaseAndWs(noCommentSql, \"DROP\") \/\/$NON-NLS-1$\r\n        || StringUtils.startsWithIgnoreCaseAndWs(noCommentSql, \"CREATE\") \/\/$NON-NLS-1$\r\n        || StringUtils.startsWithIgnoreCaseAndWs(noCommentSql, \"ALTER\")\r\n        || StringUtils.startsWithIgnoreCaseAndWs(noCommentSql, \"TRUNCATE\")\r\n        || StringUtils.startsWithIgnoreCaseAndWs(noCommentSql, \"RENAME\")) { \/\/$NON-NLS-1$\r\n\r\n      throw SQLError.createSQLException(Messages.getString(\"Statement.57\"), \/\/$NON-NLS-1$\r\n\tSQLError.SQL_STATE_ILLEGAL_ARGUMENT, getExceptionInterceptor()); \/\/$NON-NLS-1$\r\n    }\r\n  }\r\n}<\/pre>\n<p>\u56e0\u6b64\u8003\u8651\u6269\u5c55\u8bed\u6cd5\u65f6\u5728\u524d\u9762\u52a0\u4e0aSELECT\uff0c\u5982\uff1a<\/p>\n<pre lang=\"mysql\">SELECT field1,field2,... FROM UPDATE...<\/pre>\n<p>\u7136\u540e\u5c31\u53ef\u4ee5\u8d70executeQuery\u63a5\u53e3\u4e86\uff0c\u5e76\u4e14\u8fd4\u56de\u7684\u662fResultSet.<\/p>\n<h3>mysql_update<\/h3>\n<p>\u5728<a href=\"http:\/\/www.gpfeng.com\/?p=117\">\u524d\u4e00\u7bc7\u535a\u5ba2<\/a>\u4e2d\u4ecb\u7ecd\u4e86UPDATE\u8bed\u6cd5\u7684SQL\u89e3\u6790\u8fc7\u7a0b\u548c\u89e3\u6790\u7ed3\u679c\uff1a<br \/>\nset\u5de6\u503c\u96c6\u5408\uff1alex->select_lex.item_list<br \/>\nset\u53f3\u503c\u96c6\u5408\uff1alex->value_list<br \/>\nwhere\u6761\u4ef6\uff1alex->where<\/p>\n<p>\u4e0b\u9762\u5206\u6790\u4e00\u4e0bmysql_update\u7684\u6267\u884c\u8fc7\u7a0b\uff1a<\/p>\n<pre lang=\"mysql\">mysql_update\r\n|-->open_tables\r\n|-->lock_tables\r\n|-->mysql_prepare_update\r\n\r\n\/\/ \u5c06set\u5de6\u503c\u96c6\u5408fields\u7684\u5404\u4e2aItem_field\u5bf9\u8c61\u4e2d\u7684field\u6307\u5411TABLE\u4e2dfield\u6570\u7ec4\u4e2d\u7684\u5bf9\u5e94\u5730\u5740\uff0c\r\n\/\/ \u5f53\u901a\u8fc7handler\u4ece\u5b58\u50a8\u5f15\u64ce\u5c42\u83b7\u53d6\u5230\u6570\u636e\u540e\uff0cTABLE\u4e2d\u7684field\u6570\u7ec4\u4f1a\u88ab\u586b\u5145\uff0c\r\n\/\/ setup_fields\u540e\uff0c\u82e5\u66f4\u65b0fields\u5c06\u5bfc\u81f4TABLE\u4e2dfield\u88ab\u66f4\u65b0\r\n|-->setup_fields_with_no_wrap(thd, 0, fields, MARK_COLUMNS_WRITE, 0, 0) \r\n\r\n\/\/ \u5c06set\u53f3\u503c\u96c6\u5408values\u7684\u5404\u4e2aItem_field\u5bf9\u8c61\u4e2d\u7684field\u6307\u5411TABLE\u4e2dfield\u6570\u7ec4\u4e2d\u7684\u5bf9\u5e94\u5730\u5740\uff0c\r\n\/\/ \u586b\u5145\u6a21\u5f0f\u4e3aMARK_COLUMNS_READ\uff0cvalues\u4e2d\u7684\u6bcf\u4e00\u4e2a\u5bf9\u8c61\u5176\u5b9e\u662f\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\r\n|-->setup_fields(thd, 0, values, MARK_COLUMNS_READ, 0, 0)\r\n\r\n|-->open_cached_file \/\/\u4f7f\u7528IO_CACHE\u7f13\u5b58\u4ece\u5b58\u50a8\u5f15\u64ce\u5c42\u8bfb\u5230\u7684\u6ee1\u8db3where\u6761\u4ef6\u7684\u8bb0\u5f55\r\n|-->init_read_record \/\/\u6839\u636e\u5bf9where\u6761\u4ef6\u7684\u5206\u6790\u521d\u59cb\u5316\u626b\u63cf\u7269\u7406\u8bb0\u5f55\u7684\u65b9\u6cd5\r\n|-->while(info.read_record(&amp;info)) \/\/\u8bfb\u53d6\u7269\u7406\u8bb0\u5f55\uff0c\u4fdd\u5b58\u5230IO_CACHE\u4e2d\r\n    |-->found++\r\n|-->end_read_record\r\n\r\n|-->reinit_io_cache(&amp;tempfile,READ_CACHE,0L,0,0) \/\/\u5f00\u59cb\u4eceIO_CACHE\u4e2d\u8bfb\u53d6\u9700\u8981\u66f4\u65b0\u7684\u8bb0\u5f55\r\n|-->while(info.read_record(&amp;info))\r\n\r\n    \/\/ read_record\u4f1a\u5c06\u7ed3\u679c\u8bfb\u53d6\u7684\u7ed3\u679c\u586b\u5145\u5230table->record[0]\u4e2d\r\n    |-->store_record(table,record[1])\r\n\r\n    \/\/ \u8fd9\u4e00\u6b65\u5f88\u5173\u952e\uff0c\u8bfb\u53d6\u7684\u6bcf\u4e00\u884c\u8bb0\u5f55\u88ab\u89e3\u6790\u586b\u5145\u5230TABLE\u7ed3\u6784\u4e2d\u7684\u5404\u4e2afield\u4e2d\u4e86\uff0cvalues\u4e2d\u7684\u6bcf\u4e2aItem_field\r\n    \/\/ \u901a\u8fc7setup_fields\u51fd\u6570\uff0c\u5c06\u5176field\u6210\u5458\u76f4\u63a5\u6307\u5411\u4e86TABLE\u4e2d\u5bf9\u5e94\u7684field\u5730\u5740\u4e86\uff0csetup_fields(values)\r\n    \/\/ \u7684\u65b9\u5f0f\u662fMARK_COLUMNS_READ\uff0csetup_fields(fields)\u7684\u65b9\u5f0f\u662fMARK_COLUMNS_WRITE, \u56e0\u6b64\u8ba1\u7b97set\u53f3\u503c\u51fa\u6765\r\n    \/\/ \u4e4b\u540e\u8d4b\u503c\u7ed9\u5bf9\u5e94\u7684set\u5de6\u503c\uff0c\u8fd9\u6837\u5c31\u5c06TABLE\u4e2d\u5404\u4e2afield\u66f4\u65b0\u4e86\r\n    |-->fill_record_n_invoke_before_triggers(thd, fields, values, 0, table->triggers, TRG_EVENT_UPDATE)\r\n\r\n    \/\/ \u8c03\u7528\u5b58\u50a8\u5f15\u64ce\u5c42\u7684update\u51fd\u6570\uff0c\u66f4\u65b0\u4e00\u884c\u8bb0\u5f55\r\n    |-->file->ha_update_row(table->record[1], table->record[0])\r\n        |-->if (error != HA_ERR_RECORD_IS_THE_SAME) updated++\r\n|-->end_read_record\r\n\r\n|-->thd->binlog_query\r\n|-->my_ok<\/pre>\n<h3>\u9700\u8981\u4fee\u6539\u7684\u5730\u65b9<\/h3>\n<p>1. \u5728sql\/sql_yacc.yy\u4e2d\u589e\u52a0\u8bed\u6cd5\u89c4\u5219<br \/>\n\u8fd9\u91cc\u9047\u5230\u4e86\u5f88\u591a\u95ee\u9898\uff0c\u6e90\u4e8e\u7406\u8bba\u548c\u5b9e\u8df5\u8fd8\u4e0d\u591f\uff0c\u4e0d\u8fc7\u6700\u7ec8\u8fd8\u662f\u5b8c\u6210\u4e86,\u65b0\u589e\u8bed\u6cd5\uff1a<\/p>\n<pre lang=\"mysql\">GET expr1,expr2,...FROM UPDATE...<\/pre>\n<p>\u4e3a\u4ec0\u4e48\u662fGET\uff0c\u800c\u4e0d\u662f\u4e4b\u524d\u7684SELECT? \u56e0\u4e3a\u4f1a\u4e0eSELECT expr1,expr2,&#8230;FROM&#8230;\u89c4\u5219\u4ea7\u751f\u51b2\u7a81\uff0c\u56e0\u6b64\u6362\u6210\u4e86GET<strong>\uff08\u5df2\u66f4\u65b0\uff01\u89c1\u6587\u7ae0\u672b\u5c3e\uff09<\/strong>\uff0c\u4ee3\u7801\u4e2d\u589e\u52a0\uff1a<\/p>\n<p><em>sql\/sql_lex.h\u6587\u4ef6<\/em><br \/>\nsymbols\u6570\u7ec4\u4e2d\u589e\u52a0GET\u5173\u952e\u5b57\u5b9a\u4e49\uff1a<\/p>\n<pre lang=\"mysql\">{ \"GET\",    SYM(GET_SYM)},<\/pre>\n<p><em>sql\/sql_yacc.yy\u6587\u4ef6<\/em><br \/>\na)\u589e\u52a0token\u5b9a\u4e49\uff1a<\/p>\n<pre lang=\"mysql\">%token GET_SYM<\/pre>\n<p>b)\u589e\u52a0\u89c4\u5219\uff1agetupdate<\/p>\n<pre lang=\"mysql\">get_update:\r\n          GET_SYM\r\n          {\r\n            LEX *lex= Lex;\r\n            mysql_init_select(lex);\r\n          }\r\n          select_item_list FROM\r\n          UPDATE_SYM\r\n          {\r\n            LEX *lex= Lex;\r\n            lex->sql_command= SQLCOM_UPDATE;\r\n            lex->duplicates= DUP_ERROR;\r\n            lex->return_update= true;\r\n            lex->real_query_start= YYLIP->get_tok_start() - YYTHD->query();\r\n            lex->return_update_list.swap(Select->item_list);\r\n            Select->item_list.empty();\r\n          }\r\n          opt_low_priority opt_ignore table_ident\r\n          SET update_list\r\n          {\r\n            if (!Select->add_table_to_list(YYTHD, $9, NULL, \r\n                                           TL_OPTION_UPDATING, \r\n                                           TL_READ_DEFAULT,\r\n                                           MDL_SHARED_READ))\r\n              MYSQL_YYABORT;\r\n            Select->set_lock_for_tables($7);\r\n          }\r\n          where_clause opt_order_clause delete_limit_clause {}\r\n        ;<\/pre>\n<p>c) \u5728statement\u89c4\u5219\u4e2d\u589e\u52a0get_update\u5b50\u89c4\u5219(get_update\u9700\u8981\u89c4\u7ea6\u5230statement\u89c4\u5219)<\/p>\n<pre lang=\"mysql\">| get_update<\/pre>\n<p>2. \u89e3\u6790\u8bed\u6cd5\u5e76\u4fdd\u5b58select field\u5217\u8868<br \/>\nselect_item_list\u548cupdate_list\u90fd\u4f1a\u628a\u89e3\u6790\u5f97\u5230\u7684Item\u653e\u5230lex->select_lex.item_list\u4e2d\uff0c\u56e0\u6b64\u5728LEX\u7ed3\u6784\u4f53\u4e2d\u65b0\u589e\u4e86\u4e09\u4e2a\u6210\u5458<\/p>\n<pre lang=\"mysql\">+  \/*\r\n+    Impliment Oracle\/PostgreSQL's \r\n+    \"UPDATE...RETURNING...\" as \"GET...UPDATE...\"\r\n+  *\/\r\n+  bool return_update;\r\n+  List return_update_list;\r\n+  uint32 real_query_start;<\/pre>\n<p>get_update\u89c4\u5219\u5728\u89e3\u6790\u5230update_list\u4e4b\u524d\uff0c\u4f1a\u5c06\u5df2\u7ecf\u89e3\u6790\u5f97\u5230\u7684select_item\u4fdd\u5b58\u5230lex->select_lex.item_list\u4e2d\uff0c\u800c\u4e4b\u540e\u7684update_list\u89c4\u5219\u4e5f\u4f1a\u5c06set\u5de6\u503c\u4fdd\u5b58\u5728\u5176\u4e2d\uff0c\u56e0\u6b64\u5728\u89e3\u6790update_list\u4e4b\u524d\u5c06\u5176\u79fb\u5230return_update_list\u540e\u5e76\u6e05\u7a7a\u5217\u8868\uff0c\u8fd9\u6837\u5c31\u53ef\u4ee5\u5728\u6574\u4e2a\u89c4\u5219\u89e3\u6790\u5b8c\u6210\u540e\uff0c\u5206\u522b\u5f97\u5230select fields\u548cupdate fields\uff0c\u6211\u4eec\u4e0d\u5e0c\u671b\u7531\u4e8e\u65b0\u8bed\u6cd5\u7684\u6dfb\u52a0\u5f71\u54cd\u5230\u590d\u5236\u529f\u80fd\uff0c\u56e0\u6b64\u589e\u52a0real_query_start\u8bb0\u5f55\u771f\u6b63update query\u7684\u8d77\u59cb\u4f4d\u7f6e\uff0c\u6b63\u786e\u5199statement\u683c\u5f0fbinglog<\/p>\n<p>3. \u6839\u636e\u66f4\u65b0\u540e\u7684\u884c\u8bb0\u5f55\u586b\u5145select field\u5217\u8868<br \/>\n4. \u589e\u52a0update\u8fd4\u56de\u5ba2\u6237\u7aef\u7ed3\u679c\u96c6\u7684\u903b\u8f91<\/p>\n<p>\u6574\u4e2a\u8bbe\u8ba1\u5199\u5f97\u5dee\u4e0d\u591a\u4e86\uff0c3\u548c4\u6ca1\u6709\u4ec0\u4e48\u597d\u5199\u7684\uff0c\u5f88\u591a\u7ec6\u8282\u7684\u4e1c\u897f\uff0c\u5f97\u5230\u4e86select fields\u540e\u4ee5MARK_COLUMNS_READ\u8c03\u7528setup_fields\u5c31\u53ef\u4ee5\u6839\u636e\u66f4\u65b0\u540e\u884c\u4fe1\u606f\u8ba1\u7b97\u51fa\u7ed3\u679c\uff0c\u53d1\u7ed9\u5ba2\u6237\u7aef\u5c31OK\uff0c\u7a0d\u540e\u653e\u51fapatch<\/p>\n<h3>\u5b9e\u73b0\u7ed3\u679c<\/h3>\n<pre lang=\"mysql\">mysql> show create table tt\\G\r\n*************************** 1. row ***************************\r\n       Table: tt\r\nCreate Table: CREATE TABLE `tt` (\r\n  `id` int(11) NOT NULL AUTO_INCREMENT,\r\n  `a` int(11) DEFAULT NULL,\r\n  `b` int(11) DEFAULT NULL,\r\n  `c` int(11) DEFAULT NULL,\r\n  PRIMARY KEY (`id`)\r\n) ENGINE=InnoDB DEFAULT CHARSET=gbk\r\n1 row in set (0.00 sec)\r\n\r\nmysql> select * from tt;\r\n+----+------+------+------+\r\n| id | a    | b    | c    |\r\n+----+------+------+------+\r\n|  1 |    1 |    2 |    3 |\r\n|  2 |    2 |    3 |    4 |\r\n|  3 |    3 |    4 |    5 |\r\n|  4 |    4 |    5 |    6 |\r\n|  5 |    5 |    6 |    7 |\r\n|  6 |    6 |    7 |    8 |\r\n|  7 |    6 |    1 |    9 |\r\n+----+------+------+------+\r\n7 rows in set (0.00 sec)\r\n\r\nmysql> get NOW() as time, a+5 as a5, b from update tt set a=7, b=b+7 where id=7;\r\n+---------------------+------+------+\r\n| time                | a5   | b    |\r\n+---------------------+------+------+\r\n| 2013-05-24 18:08:54 |   12 |    8 |\r\n+---------------------+------+------+\r\n1 row in set (0.01 sec)\r\n\r\nmysql> select * from tt;\r\n+----+------+------+------+\r\n| id | a    | b    | c    |\r\n+----+------+------+------+\r\n|  1 |    1 |    2 |    3 |\r\n|  2 |    2 |    3 |    4 |\r\n|  3 |    3 |    4 |    5 |\r\n|  4 |    4 |    5 |    6 |\r\n|  5 |    5 |    6 |    7 |\r\n|  6 |    6 |    7 |    8 |\r\n|  7 |    7 |    8 |    9 |\r\n+----+------+------+------+\r\n7 rows in set (0.00 sec)<\/pre>\n<h3>\u6027\u80fd\u6d4b\u8bd5<\/h3>\n<p>mysql\u7684CLIENT_MULTI_STATEMENTS\u63d0\u4f9b\u4e86\u6267\u884c\u591astmt\u652f\u6301\uff0c\u672c\u6587\u5b9e\u73b0\u7684get update\u65b9\u6848\u76f8\u5bf9\u4e8eCLIENT_MULTI_STATEMENTS\u5728\u7406\u8bba\u4e0a\u51cf\u5c0f\u4e86sql parse\u7684\u4ee3\u4ef7<\/p>\n<h4>a) \u6570\u636e\u51c6\u5907<\/h4>\n<pre lang=\"mysql\">\r\nmysql> show create table t\\G\r\n*************************** 1. row ***************************\r\n       Table: t\r\nCreate Table: CREATE TABLE `t` (\r\n  `id` int(11) NOT NULL AUTO_INCREMENT,\r\n  `num` int(11) DEFAULT NULL,\r\n  `b` int(11) DEFAULT NULL,\r\n  `c` int(11) DEFAULT NULL,\r\n  `d` int(11) DEFAULT NULL,\r\n  PRIMARY KEY (`id`)\r\n) ENGINE=InnoDB AUTO_INCREMENT=16472591 DEFAULT CHARSET=gbk\r\n1 row in set (0.00 sec)\r\n\r\nmysql> select count(*) from t;\r\n+----------+\r\n| count(*) |\r\n+----------+\r\n| 16472590 |\r\n+----------+\r\n1 row in set (3.47 sec)\r\n<\/pre>\n<h4>b) \u6d4b\u8bd5\u65b9\u6cd5<\/h4>\n<pre lang=\"mysql\">\r\nmulti_statment: \r\n>id_rand=rand() % update_rows\r\n>update t set num=num+1 where id=id_rand; select num from t where id=id_rand;\r\n\r\nget_update:\r\n>id_rand=rand() % update_rows\r\n>get num from update t set num=num+1 where id=id_rand;\r\n<\/pre>\n<h4>c) \u6d4b\u8bd5\u7ed3\u679c<\/h4>\n<p><a href=\"https:\/\/i0.wp.com\/www.gpfeng.com\/wp-content\/uploads\/2013\/07\/multi_vs_getupdate.jpg\"><img decoding=\"async\" src=\"https:\/\/i0.wp.com\/www.gpfeng.com\/wp-content\/uploads\/2013\/07\/multi_vs_getupdate.jpg?w=660\" alt=\"multi_vs_getupdate\" data-recalc-dims=\"1\" \/><\/a><\/p>\n<h4>d) \u6d4b\u8bd5\u7a0b\u5e8f<\/h4>\n<p><a href=\"http:\/\/www.gpfeng.com\/wp-content\/uploads\/2013\/07\/multi_vs_getupdate.c\">multi_vs_getupdate.c<\/a><\/p>\n<p><span style=\"color: #ff0000;\"><strong>UPDATED!<\/strong><\/span><br \/>\npatch\u4e0b\u8f7d\uff1a<a href=\"http:\/\/www.gpfeng.com\/get_update.patch\">get_update.patch<\/a><\/p>\n<p><span style=\"color: #ff0000;\"><strong>UPDATED!!<\/strong><\/span><br \/>\n\u7ecf\u8fc7\u6301\u7eed\u5b66\u4e60\u548c\u5c1d\u8bd5\uff0c\u7ec8\u4e8e\u5c06GET\u66ff\u6362\u6210SELECT\u4e86\uff0c\u6700\u65b0patch\uff1a <a href=\"http:\/\/www.gpfeng.com\/wp-content\/uploads\/2014\/03\/select_update.patch_.txt\">select_update.patch<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u9700\u6c42\u63cf\u8ff0 \u6700\u8fd1\u5f00\u53d1\u63d0\u4e86\u8fd9\u6837\u4e00\u4e2a\u9700\u6c42\uff1a BEGIN; UPDATE products SET quantity= &hellip; <a href=\"http:\/\/www.gpfeng.com\/?p=134\" class=\"more-link\">\u7ee7\u7eed\u9605\u8bfb<span class=\"screen-reader-text\">Oracle\/PostgreSQL UPDATE&#8230;RETURNING&#8230;\u5728MySQL\u4e2d\u7684\u5b9e\u73b0<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false}}},"categories":[1],"tags":[],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p3tPZp-2a","jetpack_sharing_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=\/wp\/v2\/posts\/134"}],"collection":[{"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=134"}],"version-history":[{"count":39,"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=\/wp\/v2\/posts\/134\/revisions"}],"predecessor-version":[{"id":561,"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=\/wp\/v2\/posts\/134\/revisions\/561"}],"wp:attachment":[{"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=134"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=134"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=134"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}