学习笔记之postgresql

/*************************************************************************
创建人：LYK 创建时间：2019/05/05 14:47
IDE: vs2013 库版本：32位 静态库
数据库管理平台 pgAdmin III -- postgresql

注意事项：
1，添加头文件 及库文件
libpq-fe.h libpq.lib

2，电脑开启postgresql数据库服务
**************************************************************************/

void pg_test::pg_init()
{char *pghost = "127.0.0.1",*pgport = {0},*pgoptions = { 0 },*pgtty = { 0 };char  *dbName = "db_cctv";int  nFields = 0;int  i = 0;int j =0;#ifdef DEBUGFILE    *debug;
#endif  /* DEBUG */PGconn    *conn = {0};PGresult   *res = { 0 };/** Begin by setting the parameters for a backend connection.* If the parameters are NULL, the system tries to use* reasonable defaults by looking up environment variables* or, failing that, using hardwired constants.*/const char *conninfo = "postgresql://dxh:123456@localhost:5432/db_cctv";/* make a connection to the database *///conn = PQsetdb(pghost, pgport, pgoptions, pgtty, dbName);conn = PQconnectdb(conninfo);/* check to see that the backend connection was successfully made */if (PQstatus(conn) == CONNECTION_BAD){fprintf(stderr, "Connection to database '%s' failed.\n", dbName);fprintf(stderr, "%s", PQerrorMessage(conn));exit_nicely(conn);}#ifdef DEBUGdebug = fopen("/tmp/trace.out", "w");PQtrace(conn, debug);
#endif  /* DEBUG *//* start a transaction block */res = PQexec(conn, "BEGIN");if (PQresultStatus(res) != PGRES_COMMAND_OK){fprintf(stderr, "BEGIN command failed\n");PQclear(res);exit_nicely(conn);}/** should PQclear PGresult whenever it is no longer needed* so as to avoid memory leaks*/PQclear(res);/** fetch instances from the pg_database, the system catalog of* databases*/res = PQexec(conn, "DECLARE myportal CURSOR FOR select * from pg_database");if (PQresultStatus(res) != PGRES_COMMAND_OK){fprintf(stderr, "DECLARE CURSOR command failed\n");PQclear(res);exit_nicely(conn);}PQclear(res);res = PQexec(conn, "FETCH ALL in myportal");if (PQresultStatus(res) != PGRES_TUPLES_OK){fprintf(stderr, "FETCH ALL command didn't return tuples properly\n");PQclear(res);exit_nicely(conn);}/* first, print out the attribute names */nFields = PQnfields(res);for (i = 0; i < nFields; i++)printf("%-15s", PQfname(res, i));printf("\n\n");/* next, print out the instances */for (i = 0; i < PQntuples(res); i++){for (j = 0; j < nFields; j++)printf("%-15s", PQgetvalue(res, i, j));printf("\n");}PQclear(res);/* close the portal */res = PQexec(conn, "CLOSE myportal");PQclear(res);/* end the transaction */res = PQexec(conn, "END");PQclear(res);/* close the connection to the database and cleanup */PQfinish(conn);#ifdef DEBUGfclose(debug);
#endif  /* DEBUG */return ;
}

 

--创建用户dbuser 
--CREATE USER dbuser WITH PASSWORD 'password';--创建数据库
--CREATE DATABASE exampledb OWNER dbuser;--将数据库的所有权限都赋予给用户dbuser
--否则dbuser只能登陆，无法操作数据库
--GRANT ALL PRIVILEGES ON DATABASE exampledb to dbuser;--数据库操作
--CREATE TABLE user_tbl(name VARCHAR(20), signup_date DATE);--插入数据,注意字符串使用单引号，使用双引号会报错
--INSERT INTO user_tbl(name, signup_date) VALUES('张三','2019-5-6');--选择记录,显示表的所有记录
--SELECT * FROM user_tbl;--数据更新
--UPDATE user_tbl set name = '李四' WHERE name = '张三';--删除数据
--DELETE FROM user_tbl WHERE name = '李四';--添加栏位,新增列
--ALTER TABLE user_tbl ADD email VARCHAR(40); --更新结构,修改相关列的属性
--ALTER TABLE user_tbl ALTER COLUMN signup_date SET NOT NULL;--更改栏名
--ALTER TABLE user_tbl RENAME COLUMN signup_date TO signup;--删除栏
--ALTER TABLE user_tbl DROP COLUMN email;--更改表名
--ALTER TABLE user_tbl RENAME TO backup_tbl;SELECT * FROM backup_tbl;