不是就直接相加吗？你若要问程序，永远附上相关资料；若附上资料，永远用 dataex 印出资料。
1.        先 ssc install dataex (并见说明)，将原始 Stata 资料中具有”代表性”的一部分资料列出，以供有意回答者实验之用，并能提供具体操作指令。
2.        并请参考 http://www.jianshu.com/p/9870080fe769,  https://bbs.pinggu.org/thread-5048204-1-1.html, 与 https://bbs.pinggu.org/thread-5917273-1-1.html。

老师，我想让Inventory(存货）与Fixed(固定资产)相加，公司与年份一一对应，但是固定资产数据量比存货数据量多，有些公司有些年固定资产有数据，而存货没有，导致两边数据左右相加年份公司不是对应的，该怎么删除处理使之对应相加？

* Example generated by -dataex-. To install: ssc install dataex

clear

input str6 Stkcd str10 Accper double Inventory str6 E str10 F double Fixed

"000002" "2016-12-31" 468736406712.98 "000002" "2016-12-31" 8221264772.21

"000002" "2015-12-31"  368876036729.4 "000002" "2015-12-31" 5926858461.93

"000002" "2014-12-31" 318490124080.99 "000002" "2014-12-31" 3141208368.61

"000002" "2013-12-31" 331133223278.99 "000002" "2013-12-31" 2829919428.37

"000002" "2012-12-31" 255171520397.07 "000002" "2012-12-31" 2217042088.14

"000002" "2011-12-31" 208342900981.16 "000002" "2011-12-31" 2121191770.85

"000002" "2010-12-31" 133340907730.65 "000002" "2010-12-31" 1674410277.54

"000002" "2009-12-31"  90709974826.61 "000002" "2009-12-31" 1744120106.52

"000002" "2008-12-31"  87139791634.91 "000002" "2008-12-31" 1621998965.61

"000002" "2007-12-31"  66484847643.92 "000002" "2007-12-31"  883803455.98

"000002" "2006-12-31"  30817091418.49 "000002" "2006-12-31"  752073792.47

"000004" "2016-12-31"      6889468.47 "000004" "2016-12-31"   75557190.18

"000004" "2015-12-31"     249575790.7 "000004" "2015-12-31"   79241184.36

"000004" "2014-12-31"    194108869.02 "000004" "2014-12-31"   76444875.26

"000004" "2013-12-31"     81846965.23 "000004" "2013-12-31"    77074525.2

"000004" "2012-12-31"      49174638.6 "000004" "2012-12-31"    77230291.1

"000004" "2011-12-31"      41890352.5 "000004" "2011-12-31"   66100161.71

"000004" "2010-12-31"     43823442.22 "000004" "2010-12-31"   49542955.17

"000004" "2009-12-31"     68021215.45 "000004" "2009-12-31"   49700527.51

"000004" "2008-12-31"     46513519.52 "000004" "2008-12-31"   53828495.65

"000004" "2007-12-31"     33763088.54 "000004" "2007-12-31"   52055063.89

"000004" "2006-12-31"     25080292.91 "000004" "2006-12-31"   54442714.79

"000005" "2016-12-31"    426213262.54 "000005" "2016-12-31"  120441025.17

"000005" "2015-12-31"    307904455.41 "000005" "2015-12-31"  115396751.16

"000005" "2014-12-31"     15385047.58 "000005" "2014-12-31"   96560894.39

"000005" "2013-12-31"     16947537.67 "000005" "2013-12-31"   94081689.59

"000005" "2012-12-31"      16755119.5 "000005" "2012-12-31"   91603620.59

"000005" "2011-12-31"     17059162.06 "000005" "2011-12-31"   99310507.07

"000005" "2010-12-31"     55639940.54 "000005" "2010-12-31"     207518189

"000005" "2009-12-31"     38034773.63 "000005" "2009-12-31"  215915564.86

"000005" "2008-12-31"     71072218.35 "000005" "2008-12-31"  188854250.06

"000005" "2007-12-31"     81647222.55 "000005" "2007-12-31"  197721135.44

"000005" "2006-12-31"     182001299.7 "000005" "2006-12-31"  547432792.36

"000006" "2016-12-31"   7738633658.64 "000006" "2016-12-31"   13806463.94

"000006" "2015-12-31"   8444453423.11 "000006" "2015-12-31"   13357691.69

"000006" "2014-12-31"   6851796053.72 "000006" "2014-12-31"   13599062.19

"000006" "2013-12-31"   5550044639.93 "000006" "2013-12-31"   17156363.72

"000006" "2012-12-31"   5802842944.81 "000006" "2012-12-31"   16078631.36

"000006" "2011-12-31"   6277891727.69 "000006" "2011-12-31"   16078156.59

"000006" "2010-12-31"   5915003635.24 "000006" "2010-12-31"   36174540.45

"000006" "2009-12-31"   5654013059.98 "000006" "2009-12-31"   33905543.03

"000006" "2008-12-31"   5163332903.96 "000006" "2008-12-31"   51033038.78

"000006" "2007-12-31"   3613290764.15 "000006" "2007-12-31"    50018903.8

"000006" "2006-12-31"   1337100199.22 "000006" "2006-12-31"  137496949.38

"000007" "2016-12-31"       108722.49 "000007" "2016-12-31"  138147280.83

"000007" "2015-12-31"      15429192.2 "000007" "2015-12-31"  120238704.67

"000007" "2014-12-31"     17382406.51 "000007" "2014-12-31"  138134725.11

"000007" "2013-12-31"      18071808.9 "000007" "2013-12-31"  140663964.72

"000007" "2012-12-31"     18734902.17 "000007" "2012-12-31"   139984956.6

"000007" "2011-12-31"     19302039.44 "000007" "2011-12-31"  140115906.38

"000007" "2010-12-31"     19571936.46 "000007" "2010-12-31"  143279386.91

"000007" "2009-12-31"     20439680.75 "000007" "2009-12-31"  151707749.76

"000007" "2008-12-31"     20974759.23 "000007" "2008-12-31"  152154651.99

"000007" "2007-12-31"     26202863.98 "000007" "2007-12-31"  285787834.56

"000007" "2006-12-31"     87752835.96 "000007" "2006-12-31"  500514487.62

"000008" "2016-12-31"    583387717.87 "000008" "2016-12-31"  262907769.91

"000008" "2015-12-31"    308920753.18 "000008" "2015-12-31"  714514812.14

"000008" "2014-12-31"      8691239.34 "000008" "2014-12-31"  534122471.27

"000008" "2013-12-31"       9682765.4 "000008" "2013-12-31"  541507654.53

"000008" "2012-12-31"     10699817.15 "000008" "2012-12-31"  535755035.94

"000008" "2011-12-31"       287627.95 "000008" "2011-12-31"    4702348.19

"000008" "2010-12-31"       154575.17 "000008" "2010-12-31"    4768836.42

"000008" "2006-12-31"               . "000008" "2009-12-31"    4497636.42

"000009" "2016-12-31"   7887941371.86 "000008" "2008-12-31"   10937115.37

"000009" "2015-12-31"   6308077975.45 "000008" "2007-12-31"   11244465.37

"000009" "2014-12-31"    6176122159.8 "000008" "2006-12-31"   57164041.56

"000009" "2013-12-31"   5690840021.65 "000009" "2016-12-31" 3805187224.82

"000009" "2012-12-31"   5585585407.32 "000009" "2015-12-31"  2894912556.2

"000009" "2011-12-31"   5620839193.23 "000009" "2014-12-31" 2164273109.51

"000009" "2010-12-31"   4196855915.11 "000009" "2013-12-31"  2004379212.2

"000009" "2009-12-31"   2128572202.53 "000009" "2012-12-31" 1496336536.66

"000009" "2008-12-31"   2336389808.69 "000009" "2011-12-31" 1348379598.86

"000009" "2007-12-31"   2139513231.53 "000009" "2010-12-31" 1231507670.32

"000009" "2006-12-31"   2499962349.43 "000009" "2009-12-31" 1257857414.82

end

* Example generated by -dataex-. To install: ssc install dataex
clear
input str6 Stkcd str10 Accper double Inventory str6 E str10 F double Fixed
"000002" "2016-12-31" 468736406712.98 "000002" "2016-12-31" 8221264772.21
"000002" "2015-12-31"  368876036729.4 "000002" "2015-12-31" 5926858461.93
"000002" "2014-12-31" 318490124080.99 "000002" "2014-12-31" 3141208368.61
"000002" "2013-12-31" 331133223278.99 "000002" "2013-12-31" 2829919428.37
"000002" "2012-12-31" 255171520397.07 "000002" "2012-12-31" 2217042088.14
"000002" "2011-12-31" 208342900981.16 "000002" "2011-12-31" 2121191770.85
"000002" "2010-12-31" 133340907730.65 "000002" "2010-12-31" 1674410277.54
"000002" "2009-12-31"  90709974826.61 "000002" "2009-12-31" 1744120106.52
"000002" "2008-12-31"  87139791634.91 "000002" "2008-12-31" 1621998965.61
"000002" "2007-12-31"  66484847643.92 "000002" "2007-12-31"  883803455.98
"000002" "2006-12-31"  30817091418.49 "000002" "2006-12-31"  752073792.47
"000004" "2016-12-31"      6889468.47 "000004" "2016-12-31"   75557190.18
"000004" "2015-12-31"     249575790.7 "000004" "2015-12-31"   79241184.36
"000004" "2014-12-31"    194108869.02 "000004" "2014-12-31"   76444875.26
"000004" "2013-12-31"     81846965.23 "000004" "2013-12-31"    77074525.2
"000004" "2012-12-31"      49174638.6 "000004" "2012-12-31"    77230291.1
"000004" "2011-12-31"      41890352.5 "000004" "2011-12-31"   66100161.71
"000004" "2010-12-31"     43823442.22 "000004" "2010-12-31"   49542955.17
"000004" "2009-12-31"     68021215.45 "000004" "2009-12-31"   49700527.51
"000004" "2008-12-31"     46513519.52 "000004" "2008-12-31"   53828495.65
"000004" "2007-12-31"     33763088.54 "000004" "2007-12-31"   52055063.89
"000004" "2006-12-31"     25080292.91 "000004" "2006-12-31"   54442714.79
"000005" "2016-12-31"    426213262.54 "000005" "2016-12-31"  120441025.17
"000005" "2015-12-31"    307904455.41 "000005" "2015-12-31"  115396751.16
"000005" "2014-12-31"     15385047.58 "000005" "2014-12-31"   96560894.39
"000005" "2013-12-31"     16947537.67 "000005" "2013-12-31"   94081689.59
"000005" "2012-12-31"      16755119.5 "000005" "2012-12-31"   91603620.59
"000005" "2011-12-31"     17059162.06 "000005" "2011-12-31"   99310507.07
"000005" "2010-12-31"     55639940.54 "000005" "2010-12-31"     207518189
"000005" "2009-12-31"     38034773.63 "000005" "2009-12-31"  215915564.86
"000005" "2008-12-31"     71072218.35 "000005" "2008-12-31"  188854250.06
"000005" "2007-12-31"     81647222.55 "000005" "2007-12-31"  197721135.44
"000005" "2006-12-31"     182001299.7 "000005" "2006-12-31"  547432792.36
"000006" "2016-12-31"   7738633658.64 "000006" "2016-12-31"   13806463.94
"000006" "2015-12-31"   8444453423.11 "000006" "2015-12-31"   13357691.69
"000006" "2014-12-31"   6851796053.72 "000006" "2014-12-31"   13599062.19
"000006" "2013-12-31"   5550044639.93 "000006" "2013-12-31"   17156363.72
"000006" "2012-12-31"   5802842944.81 "000006" "2012-12-31"   16078631.36
"000006" "2011-12-31"   6277891727.69 "000006" "2011-12-31"   16078156.59
"000006" "2010-12-31"   5915003635.24 "000006" "2010-12-31"   36174540.45
"000006" "2009-12-31"   5654013059.98 "000006" "2009-12-31"   33905543.03
"000006" "2008-12-31"   5163332903.96 "000006" "2008-12-31"   51033038.78
"000006" "2007-12-31"   3613290764.15 "000006" "2007-12-31"    50018903.8
"000006" "2006-12-31"   1337100199.22 "000006" "2006-12-31"  137496949.38
"000007" "2016-12-31"       108722.49 "000007" "2016-12-31"  138147280.83
"000007" "2015-12-31"      15429192.2 "000007" "2015-12-31"  120238704.67
"000007" "2014-12-31"     17382406.51 "000007" "2014-12-31"  138134725.11
"000007" "2013-12-31"      18071808.9 "000007" "2013-12-31"  140663964.72
"000007" "2012-12-31"     18734902.17 "000007" "2012-12-31"   139984956.6
"000007" "2011-12-31"     19302039.44 "000007" "2011-12-31"  140115906.38
"000007" "2010-12-31"     19571936.46 "000007" "2010-12-31"  143279386.91
"000007" "2009-12-31"     20439680.75 "000007" "2009-12-31"  151707749.76
"000007" "2008-12-31"     20974759.23 "000007" "2008-12-31"  152154651.99
"000007" "2007-12-31"     26202863.98 "000007" "2007-12-31"  285787834.56
"000007" "2006-12-31"     87752835.96 "000007" "2006-12-31"  500514487.62
"000008" "2016-12-31"    583387717.87 "000008" "2016-12-31"  262907769.91
"000008" "2015-12-31"    308920753.18 "000008" "2015-12-31"  714514812.14
"000008" "2014-12-31"      8691239.34 "000008" "2014-12-31"  534122471.27
"000008" "2013-12-31"       9682765.4 "000008" "2013-12-31"  541507654.53
"000008" "2012-12-31"     10699817.15 "000008" "2012-12-31"  535755035.94
"000008" "2011-12-31"       287627.95 "000008" "2011-12-31"    4702348.19
"000008" "2010-12-31"       154575.17 "000008" "2010-12-31"    4768836.42
"000008" "2006-12-31"               . "000008" "2009-12-31"    4497636.42
"000009" "2016-12-31"   7887941371.86 "000008" "2008-12-31"   10937115.37
"000009" "2015-12-31"   6308077975.45 "000008" "2007-12-31"   11244465.37
"000009" "2014-12-31"    6176122159.8 "000008" "2006-12-31"   57164041.56
"000009" "2013-12-31"   5690840021.65 "000009" "2016-12-31" 3805187224.82
"000009" "2012-12-31"   5585585407.32 "000009" "2015-12-31"  2894912556.2
"000009" "2011-12-31"   5620839193.23 "000009" "2014-12-31" 2164273109.51
"000009" "2010-12-31"   4196855915.11 "000009" "2013-12-31"  2004379212.2
"000009" "2009-12-31"   2128572202.53 "000009" "2012-12-31" 1496336536.66
"000009" "2008-12-31"   2336389808.69 "000009" "2011-12-31" 1348379598.86
"000009" "2007-12-31"   2139513231.53 "000009" "2010-12-31" 1231507670.32
"000009" "2006-12-31"   2499962349.43 "000009" "2009-12-31" 1257857414.82
end

哪里不一样？

老师，我用merge匹配上了，谢谢。