IBM Informix ESQL/C Programmers Manual读书笔记（二）
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posted @ 2012年3月13日 23:13
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 | /* Informix数据类型常量，均定义在sqltypes.h文件中。 * 包括SQL数据类型常量。宿主C语言数据类型，例如 * double CDOUBLETYPE 105 * dec_t or decimal CDECIMALTYPE 107 * fixchar CFIXCHARTYPE 108 * string CSTRINGTYPE 109 * date CDATETYPE 110 * dec_t or decimal CMONEYTYPE 111 * datetime or dtime_t CDTIMETYPE 112 * ifx_loc_t or loc_t CLOCATORTYPE 113*//*当两个数据的类型不一致时，Informix会自动转换他们的类型。1，比较。例如 CHAR 邮编与 INT整型比对。2，Fetch or insert3，算数运算。*//* C TO N或 N TO C空间不足时，sqlca.sqlwarn.sqlwarn1值为W，且SQLSTATE值为 * 01004。 * BOOLEAN TO C时，BOOLEAN值'\01','\00'自动转换为FIXCHAR值 'T'或'F'。 * * 算术转换： * Operand Type Convert To * FLOAT DECIMAL(17) * SMALLFLOAT DECIMAL(9) * INTEGER DECIMAL(10,0) * SMALLINT DECIMAL(5,0) For example, for an arithmetic operation between a fixed-point decimal of DECIMAL(8,3) and a FLOAT value, Informix ESQL/C converts the FLOAT value to a floating-point decimal of DECIMAL(17). The arithmetic result has a data type of DECIMAL(17). Function Name Description SeeThe risnull() Checks whether a C variable is null B-191The rsetnull() Sets a C variable to null B-197The rtypalign() Aligns data on correct type boundaries B-206The rtypmsize() Gives the byte size of SQL data types B-209The rtypname() Returns the name of a specified SQL data type B-211The rtypwidth() Returns the minimum number of characters that a characterdata type needs to avoid truncation *//* * This section describes the characteristics of these data types and the differences *among them. * Table 4-1. ESQL/C Character Data Types * ESQL/C Character Data Type Null Terminated Contains Trailing Blanks * char Y Y * fixchar N Y * string Y Returns a trailing blank only if the column contains an empty string. * varchar Y Y * lvarchar Y */你可以将带有\0结束符的C字符串放入FIXCHAR变量（空间要够大）。但这不是一个好主意，当数据库服务器将这个FIXCHAR放入列中时，终结符也被放入。/* * When the IFX_PAD_VARCHAR environment variable is set to 1, the client sends * the VARCHAR data type with padded trailing spaces. When this environment is * not set (the default), the client sends the VARCHAR data type value without * trailing spaces. The IFX_PAD_VARCHAR environment variable must be set only at * the client side and is supported only with IBM Informix ESQL/C Version 9.53 and * 2.90 or later and IBM Informix Version 9.40 or later. * */如果你不指定lvarchar宿主变量的大小，它等同于一字节的char类型。如果指定size，等同于C语言同等大小的CHAR类型。如果lvarchar宿主变量是一个指针，指针指向的数据最大可以2GB。lvarchar类型设计为当你insert和select用户自定义或不明类型时，可以表现为字符串格式。必须使用 ifx_var() 函数操作lvarchar指针。/* An application can fetch data from a database column of type CHAR or * VARCHAR into a character (char, string, fixchar, varchar, or lvarchar) host * variable. If the column data does not fit into the character host variable, * Informix ESQL/C truncates the data. To notify the user of the truncation, * Informix ESQL/C performs the following actions: It sets the * sqlca.sqlwarn.sqlwarn1 warning flag to W and the SQLSTATE variable to * 01004. It sets any indicator variable that is associated with the * character host variable to the size of the character data in the column. * * * Inserting CHAR Data An application can insert data from a character host * variable (char, string, fixchar, varchar, or lvarchar) into a database * column of type CHAR. If the value is shorter than the size of the database * column then the database server pads the value with blanks up to the size * of the column. If the value is longer than the size of the column the * database server truncates the value if the database is non-ANSI. No warning * is generated when this truncation occurs. If the database is ANSI and the * value is longer than the column size then the insert fails and this error * is returned: -1279: Value exceeds string column length. * *//* 以by函数开头的函数操作和返回fixed-length字符串。 * 以rst和st（除了stchar)开头的函数，操作或返回终结符结尾的字符串。 * rdownshit和rupshit操作有终结符的字符串，但是不返回值。 */Function Name Descriptionbycmpr() Compares two groups of contiguous bytes B-10bycopy() Copies bytes from one area to another B-12byfill() Fills an area you specify with a character B-13byleng() Counts the number of bytes in a string B-14ldchar() Copies a fixed-length string to a null-terminated string B-170rdownshift() Converts all letters to lowercase B-176rstod() Converts a string to a double value B-200rstoi() Converts a string to a short integer value B-201rstol() Converts a string to a 4-byte integer value B-202rupshift() Converts all letters to uppercase B-209stcat() Concatenates one string to another B-232stchar() Copies a null-terminated string to a fixed-length string B-233stcmpr() Compares two strings B-234stcopy() Copies one string to another string B-235stleng() Counts the number of bytes in a string B-235 |
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